{"id":617,"date":"2021-07-23T09:20:14","date_gmt":"2021-07-23T13:20:14","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/aperrott\/chapter\/intermolecular-forces\/"},"modified":"2022-06-23T09:08:28","modified_gmt":"2022-06-23T13:08:28","slug":"intermolecular-forces","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/aperrott\/chapter\/intermolecular-forces\/","title":{"raw":"10.1 Intermolecular Forces","rendered":"10.1 Intermolecular Forces"},"content":{"raw":"<div class=\"textbox textbox--learning-objectives\">\r\n<h3><strong>Learning Objectives<\/strong><\/h3>\r\nBy the end of this section, you will be able to:\r\n<ul>\r\n \t<li>Describe the types of intermolecular forces possible between atoms or molecules in condensed phases (dispersion forces, dipole-dipole attractions, and hydrogen bonding)<\/li>\r\n \t<li>Identify the types of intermolecular forces experienced by specific molecules based on their structures<\/li>\r\n \t<li>Explain the relation between the intermolecular forces present within a substance and the temperatures associated with changes in its physical state<\/li>\r\n<\/ul>\r\n<\/div>\r\n<p id=\"fs-idp55691520\">As was the case for gaseous substances, the kinetic molecular theory may be used to explain the behavior of solids and liquids. In the following description, the term <em data-effect=\"italics\">particle<\/em> will be used to refer to an atom, molecule, or ion. Note that we will use the popular phrase \u201cintermolecular attraction\u201d to refer to attractive forces between the particles of a substance, regardless of whether these particles are molecules, atoms, or ions.<\/p>\r\n<p id=\"fs-idp57413920\">Consider these two aspects of the molecular-level environments in solid, liquid, and gaseous matter:<\/p>\r\n\r\n<ul id=\"fs-idm45003248\" data-bullet-style=\"bullet\">\r\n \t<li>Particles in a solid are tightly packed together and often arranged in a regular pattern; in a liquid, they are close together with no regular arrangement; in a gas, they are far apart with no regular arrangement.<\/li>\r\n \t<li>Particles in a solid vibrate about fixed positions and do not generally move in relation to one another; in a liquid, they move past each other but remain in essentially constant contact; in a gas, they move independently of one another except when they collide.<\/li>\r\n<\/ul>\r\n<p id=\"fs-idm53508384\">The differences in the properties of a solid, liquid, or gas reflect the strengths of the attractive forces between the atoms, molecules, or ions that make up each phase. The phase in which a substance exists depends on the relative extents of its <strong>intermolecular forces (IMFs)<\/strong> and the kinetic energies (KE) of its molecules. IMFs are the various forces of attraction that may exist between the atoms and molecules of a substance due to electrostatic phenomena, as will be detailed in this module. These forces serve to hold particles close together, whereas the particles\u2019 KE provides the energy required to overcome the attractive forces and thus increase the distance between particles. <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_KMTPhases1\">(Figure)<\/a> illustrates how changes in physical state may be induced by changing the temperature, hence, the average KE, of a given substance.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_KMTPhases1\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">Transitions between solid, liquid, and gaseous states of a substance occur when conditions of temperature or pressure favor the associated changes in intermolecular forces. (Note: The space between particles in the gas phase is much greater than shown.)<\/div>\r\n<span id=\"fs-idp1251008\" data-type=\"media\" data-alt=\"Three sealed flasks are labeled, \u201cCrystalline solid,\u201d \u201cLiquid,\u201d and \u201cGas,\u201d from left to right. The first flask holds a cube composed of small spheres sitting on the bottom while the second flask shows a lot of small spheres in the bottom that are spaced a small distance apart from one another and have lines around them to indicate motion. The third flask shows a few spheres spread far from one another with larger lines to indicate motion. There is a right-facing arrow that spans the top of all three flasks. The arrow is labeled, \u201cIncreasing K E ( temperature ).\u201d There is a left-facing arrow that spans the bottom of all three flasks. The arrow is labeled, \u201cIncreasing I M F.\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_KMTPhases1-1.jpg\" alt=\"Three sealed flasks are labeled, \u201cCrystalline solid,\u201d \u201cLiquid,\u201d and \u201cGas,\u201d from left to right. The first flask holds a cube composed of small spheres sitting on the bottom while the second flask shows a lot of small spheres in the bottom that are spaced a small distance apart from one another and have lines around them to indicate motion. The third flask shows a few spheres spread far from one another with larger lines to indicate motion. There is a right-facing arrow that spans the top of all three flasks. The arrow is labeled, \u201cIncreasing K E ( temperature ).\u201d There is a left-facing arrow that spans the bottom of all three flasks. The arrow is labeled, \u201cIncreasing I M F.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idm190830512\">As an example of the processes depicted in this figure, consider a sample of water. When gaseous water is cooled sufficiently, the attractions between H<sub>2<\/sub>O molecules will be capable of holding them together when they come into contact with each other; the gas condenses, forming liquid H<sub>2<\/sub>O. For example, liquid water forms on the outside of a cold glass as the water vapor in the air is cooled by the cold glass, as seen in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_WaterPhase\">(Figure)<\/a>.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_WaterPhase\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">Condensation forms when water vapor in the air is cooled enough to form liquid water, such as (a) on the outside of a cold beverage glass or (b) in the form of fog. (credit a: modification of work by Jenny Downing; credit b: modification of work by Cory Zanker)<\/div>\r\n<span id=\"fs-idp51997104\" data-type=\"media\" data-alt=\"Image a shows a brown colored beverage in a glass with condensation on the outside. Image b shows a body of water with fog hovering above the surface of the water.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_WaterPhase-1.jpg\" alt=\"Image a shows a brown colored beverage in a glass with condensation on the outside. Image b shows a body of water with fog hovering above the surface of the water.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idm59044480\">We can also liquefy many gases by compressing them, if the temperature is not too high. The increased pressure brings the molecules of a gas closer together, such that the attractions between the molecules become strong relative to their KE. Consequently, they form liquids. Butane, C<sub>4<\/sub>H<sub>10<\/sub>, is the fuel used in disposable lighters and is a gas at standard temperature and pressure. Inside the lighter\u2019s fuel compartment, the butane is compressed to a pressure that results in its condensation to the liquid state, as shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_ButanePhase\">(Figure)<\/a>.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_ButanePhase\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">Gaseous butane is compressed within the storage compartment of a disposable lighter, resulting in its condensation to the liquid state. (credit: modification of work by \u201cSam-Cat\u201d\/Flickr)<\/div>\r\n<span id=\"fs-idp136258192\" data-type=\"media\" data-alt=\"A butane lighter is shown.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_ButanePhase-1.jpg\" alt=\"A butane lighter is shown.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idm68544288\">Finally, if the temperature of a liquid becomes sufficiently low, or the pressure on the liquid becomes sufficiently high, the molecules of the liquid no longer have enough KE to overcome the IMF between them, and a solid forms. A more thorough discussion of these and other changes of state, or phase transitions, is provided in a later module of this chapter.<\/p>\r\n\r\n<div id=\"fs-idp144602800\" class=\"chemistry link-to-learning\" data-type=\"note\">\r\n<p id=\"fs-idp70176880\">Access this <a href=\"http:\/\/openstaxcollege.org\/l\/16phetvisual\">interactive simulation<\/a> on states of matter, phase transitions, and intermolecular forces. This simulation is useful for visualizing concepts introduced throughout this chapter.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idp48705360\" class=\"bc-section section\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><strong>Forces between Molecules<\/strong><\/h3>\r\n<p id=\"fs-idp15601504\">Under appropriate conditions, the attractions between all gas molecules will cause them to form liquids or solids. This is due to intermolecular forces, not <em data-effect=\"italics\">intra<\/em>molecular forces. <em data-effect=\"italics\">Intra<\/em>molecular forces are those <em data-effect=\"italics\">within<\/em> the molecule that keep the molecule together, for example, the bonds between the atoms. <em data-effect=\"italics\">Inter<\/em>molecular forces are the attractions <em data-effect=\"italics\">between<\/em> molecules, which determine many of the physical properties of a substance. <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_IntravInter\">(Figure)<\/a> illustrates these different molecular forces. The strengths of these attractive forces vary widely, though usually the IMFs between small molecules are weak compared to the intramolecular forces that bond atoms together within a molecule. For example, to overcome the IMFs in one mole of liquid HCl and convert it into gaseous HCl requires only about 17 kJ. However, to break the covalent bonds between the hydrogen and chlorine atoms in one mole of HCl requires about 25 times more energy\u2014430 kJ.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_IntravInter\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\"><em data-effect=\"italics\">Intra<\/em>molecular forces keep a molecule intact. <em data-effect=\"italics\">Inter<\/em>molecular forces hold multiple molecules together and determine many of a substance\u2019s properties.<\/div>\r\n<span id=\"fs-idm297424\" data-type=\"media\" data-alt=\"An image is shown in which two molecules composed of a green sphere labeled \u201cC l\u201d connected on the right to a white sphere labeled \u201cH\u201d are near one another with a dotted line labeled \u201cIntermolecular force ( weak )\u201d drawn between them. A line connects the two spheres in each molecule and the line is labeled \u201cIntramolecular force ( strong ).\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_IntravInter-1.jpg\" alt=\"An image is shown in which two molecules composed of a green sphere labeled \u201cC l\u201d connected on the right to a white sphere labeled \u201cH\u201d are near one another with a dotted line labeled \u201cIntermolecular force ( weak )\u201d drawn between them. A line connects the two spheres in each molecule and the line is labeled \u201cIntramolecular force ( strong ).\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idm68677744\">All of the attractive forces between neutral atoms and molecules are known as <span data-type=\"term\">van der Waals forces<\/span>, although they are usually referred to more informally as intermolecular attraction. We will consider the various types of IMFs in the next three sections of this module.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm146733840\" class=\"bc-section section\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><strong>Dispersion Forces<\/strong><\/h3>\r\n<p id=\"fs-idp26129792\">One of the three van der Waals forces is present in all condensed phases, regardless of the nature of the atoms or molecules composing the substance. This attractive force is called the <strong><span class=\"no-emphasis\" data-type=\"term\">London dispersion force<\/span><\/strong> in honor of German-born American physicist Fritz <span class=\"no-emphasis\" data-type=\"term\">London<\/span> who, in 1928, first explained it. This force is often referred to as simply the <span data-type=\"term\">dispersion force<\/span>. Because the electrons of an atom or molecule are in constant motion (or, alternatively, the electron\u2019s location is subject to quantum-mechanical variability), at any moment in time, an atom or molecule can develop a temporary, <span data-type=\"term\">instantaneous dipole<\/span> if its electrons are distributed asymmetrically. The presence of this dipole can, in turn, distort the electrons of a neighboring atom or molecule, producing an <span data-type=\"term\">induced dipole<\/span>. These two rapidly fluctuating, temporary dipoles thus result in a relatively weak electrostatic attraction between the species\u2014a so-called dispersion force like that illustrated in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_DispForces\">(Figure)<\/a>.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_DispForces\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">Dispersion forces result from the formation of temporary dipoles, as illustrated here for two nonpolar diatomic molecules.<\/div>\r\n<span id=\"fs-idp52348576\" data-type=\"media\" data-alt=\"Two pairs of molecules are shown where each molecule has one larger blue side labeled \u201cdelta sign, negative sign\u201d and a smaller red side labeled \u201cdelta sign, positive sign.\u201d Toward the middle of the both molecules, but still on each distinct side, is a black dot. Between the two images is a dotted line labeled, \u201cAttractive force.\u201d In the first image, the red and blue sides are labeled, \u201cUnequal distribution of electrons.\u201d Below both images are brackets. The brackets are labeled, \u201cTemporary dipoles.\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_DispForces-1.jpg\" alt=\"Two pairs of molecules are shown where each molecule has one larger blue side labeled \u201cdelta sign, negative sign\u201d and a smaller red side labeled \u201cdelta sign, positive sign.\u201d Toward the middle of the both molecules, but still on each distinct side, is a black dot. Between the two images is a dotted line labeled, \u201cAttractive force.\u201d In the first image, the red and blue sides are labeled, \u201cUnequal distribution of electrons.\u201d Below both images are brackets. The brackets are labeled, \u201cTemporary dipoles.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idm80968928\">Dispersion forces that develop between atoms in different molecules can attract the two molecules to each other. The forces are relatively weak, however, and become significant only when the molecules are very close. Larger and heavier atoms and molecules exhibit stronger dispersion forces than do smaller and lighter atoms and molecules. F<sub>2<\/sub> and Cl<sub>2<\/sub> are gases at room temperature (reflecting weaker attractive forces); Br<sub>2<\/sub> is a liquid, and I<sub>2<\/sub> is a solid (reflecting stronger attractive forces). Trends in observed melting and boiling points for the halogens clearly demonstrate this effect, as seen in <a class=\"autogenerated-content\" href=\"#fs-idp55860464\">(Figure)<\/a>.<\/p>\r\n\r\n<table id=\"fs-idp55860464\" class=\"top-titled\" summary=\"This table has six rows and five columns. The first row is a header row and it labels each column: \u201cHalogen,\u201d \u201cMolar Mass,\u201d \u201cAtomic Radius,\u201d \u201cMelting Point,\u201d and \u201cBoiling Point.\u201d Under the \u201cHalogen\u201d column are the following: Fluorine, F subscript 2; Chlorine, C l subscript 2; bromine, B r subscript 2; iodine, I subscript 2; astatine, A t subscript 2. Under the \u201cMolar Mass\u201d column are the following: 38 g \/ mol; 71 g \/ mol; 160 g \/ mol; 254 g \/ mol; 420 g \/ mol. Under the \u201cAtomic Radius\u201d column are the following: 72 p m; 99 p m; 114 p m; 133 p m; 150 p m. Under the \u201cMelting Point\u201d column are the following: 53 K; 172 K; 266 K; 387 K; and 575 K. Under the \u201cBoiling Point\u201d column are the following: 85 K; 238 K; 332 K; 457 K; and 610 K.\">\r\n<thead>\r\n<tr valign=\"middle\">\r\n<th colspan=\"5\" data-align=\"center\">Melting and Boiling Points of the Halogens<\/th>\r\n<\/tr>\r\n<tr valign=\"middle\">\r\n<th data-align=\"center\">Halogen<\/th>\r\n<th data-align=\"center\">Molar Mass<\/th>\r\n<th data-align=\"center\">Atomic Radius<\/th>\r\n<th data-align=\"center\">Melting Point<\/th>\r\n<th data-align=\"center\">Boiling Point<\/th>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr valign=\"middle\">\r\n<td data-align=\"center\">fluorine, F<sub>2<\/sub><\/td>\r\n<td data-align=\"center\">38 g\/mol<\/td>\r\n<td data-align=\"center\">72 pm<\/td>\r\n<td data-align=\"center\">53 K<\/td>\r\n<td data-align=\"center\">85 K<\/td>\r\n<\/tr>\r\n<tr valign=\"middle\">\r\n<td data-align=\"center\">chlorine, Cl<sub>2<\/sub><\/td>\r\n<td data-align=\"center\">71 g\/mol<\/td>\r\n<td data-align=\"center\">99 pm<\/td>\r\n<td data-align=\"center\">172 K<\/td>\r\n<td data-align=\"center\">238 K<\/td>\r\n<\/tr>\r\n<tr valign=\"middle\">\r\n<td data-align=\"center\">bromine, Br<sub>2<\/sub><\/td>\r\n<td data-align=\"center\">160 g\/mol<\/td>\r\n<td data-align=\"center\">114 pm<\/td>\r\n<td data-align=\"center\">266 K<\/td>\r\n<td data-align=\"center\">332 K<\/td>\r\n<\/tr>\r\n<tr valign=\"middle\">\r\n<td data-align=\"center\">iodine, I<sub>2<\/sub><\/td>\r\n<td data-align=\"center\">254 g\/mol<\/td>\r\n<td data-align=\"center\">133 pm<\/td>\r\n<td data-align=\"center\">387 K<\/td>\r\n<td data-align=\"center\">457 K<\/td>\r\n<\/tr>\r\n<tr valign=\"middle\">\r\n<td data-align=\"center\">astatine, At<sub>2<\/sub><\/td>\r\n<td data-align=\"center\">420 g\/mol<\/td>\r\n<td data-align=\"center\">150 pm<\/td>\r\n<td data-align=\"center\">575 K<\/td>\r\n<td data-align=\"center\">610 K<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<p id=\"fs-idm135149056\">The increase in melting and boiling points with increasing atomic\/molecular size may be rationalized by considering how the strength of dispersion forces is affected by the electronic structure of the atoms or molecules in the substance. In a larger atom, the valence electrons are, on average, farther from the nuclei than in a smaller atom. Thus, they are less tightly held and can more easily form the temporary dipoles that produce the attraction. The measure of how easy or difficult it is for another electrostatic charge (for example, a nearby ion or polar molecule) to distort a molecule\u2019s charge distribution (its electron cloud) is known as <strong>polarizability<\/strong>. A molecule that has a charge cloud that is easily distorted is said to be very polarizable and will have large dispersion forces; one with a charge cloud that is difficult to distort is not very polarizable and will have small dispersion forces.<\/p>\r\n\r\n<div id=\"fs-idm100317728\" class=\"textbox textbox--examples\" data-type=\"example\">\r\n<p id=\"fs-idp26427152\"><strong>London Forces and Their Effects<\/strong><\/p>\r\nOrder the following compounds of a group 14 element and hydrogen from lowest to highest boiling point: CH<sub>4<\/sub>, SiH<sub>4<\/sub>, GeH<sub>4<\/sub>, and SnH<sub>4<\/sub>. Explain your reasoning.\r\n<p id=\"fs-idm106734480\"><span data-type=\"title\">Solution:<\/span><\/p>\r\nApplying the skills acquired in the chapter on chemical bonding and molecular geometry, all of these compounds are predicted to be nonpolar, so they may experience only dispersion forces: the smaller the molecule, the less polarizable and the weaker the dispersion forces; the larger the molecule, the larger the dispersion forces. The molar masses of CH<sub>4<\/sub>, SiH<sub>4<\/sub>, GeH<sub>4<\/sub>, and SnH<sub>4<\/sub> are approximately 16 g\/mol, 32 g\/mol, 77 g\/mol, and 123 g\/mol, respectively. Therefore, CH<sub>4<\/sub> is expected to have the lowest boiling point and SnH<sub>4<\/sub> the highest boiling point. The ordering from lowest to highest boiling point is expected to be CH<sub>4<\/sub> &lt; SiH<sub>4<\/sub> &lt; GeH<sub>4<\/sub> &lt; SnH<sub>4<\/sub>.\r\n<p id=\"fs-idp136003920\">A graph of the actual boiling points of these compounds versus the period of the group 14 element shows this prediction to be correct:<\/p>\r\n<span id=\"fs-idp63841152\" class=\"scaled-down\" data-type=\"media\" data-alt=\"A line graph, titled \u201cCarbon Family,\u201d is shown where the y-axis is labeled \u201cTemperature, ( degree sign C )\u201d and has values of \u201cnegative 200\u201d to \u201cnegative 40\u201d from bottom to top in increments of 20. The x-axis is labeled \u201cPeriod\u201d and has values of \u201c0\u201d to \u201c5\u201d in increments of 1. The first point on the graph is labeled \u201cC H subscript 4\u201d and is at point \u201c2, negative 160.\u201d The second point on the graph is labeled \u201cS i H subscript 4\u201d and is at point \u201c3, negative 120\u201d while the third point on the graph is labeled \u201cG e H subscript 4\u201d and is at point \u201c4, negative 100.\u201d The fourth point on the graph is labeled \u201cS n H subscript 4\u201d and is at point \u201c5, negative 60.\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_BoilPoints_img-1.jpg\" alt=\"A line graph, titled \u201cCarbon Family,\u201d is shown where the y-axis is labeled \u201cTemperature, ( degree sign C )\u201d and has values of \u201cnegative 200\u201d to \u201cnegative 40\u201d from bottom to top in increments of 20. The x-axis is labeled \u201cPeriod\u201d and has values of \u201c0\u201d to \u201c5\u201d in increments of 1. The first point on the graph is labeled \u201cC H subscript 4\u201d and is at point \u201c2, negative 160.\u201d The second point on the graph is labeled \u201cS i H subscript 4\u201d and is at point \u201c3, negative 120\u201d while the third point on the graph is labeled \u201cG e H subscript 4\u201d and is at point \u201c4, negative 100.\u201d The fourth point on the graph is labeled \u201cS n H subscript 4\u201d and is at point \u201c5, negative 60.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n<p id=\"fs-idp128687200\"><strong>Check Your Learning:<\/strong><\/p>\r\nOrder the following hydrocarbons from lowest to highest boiling point: C<sub>2<\/sub>H<sub>6<\/sub>, C<sub>3<\/sub>H<sub>8<\/sub>, and C<sub>4<\/sub>H<sub>10<\/sub>.\r\n\r\n&nbsp;\r\n<div id=\"fs-idm119929280\" data-type=\"note\">\r\n<div data-type=\"title\"><strong>Answer:<\/strong><\/div>\r\n<p id=\"fs-idm93042944\">C<sub>2<\/sub>H<sub>6<\/sub> &lt; C<sub>3<\/sub>H<sub>8<\/sub> &lt; C<sub>4<\/sub>H<sub>10<\/sub>. All of these compounds are nonpolar and only have London dispersion forces: the larger the molecule, the larger the dispersion forces and the higher the boiling point. The ordering from lowest to highest boiling point is therefore C<sub>2<\/sub>H<sub>6<\/sub> &lt; C<sub>3<\/sub>H<sub>8<\/sub> &lt; C<sub>4<\/sub>H<sub>10<\/sub>.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<p id=\"fs-idm93742928\">The shapes of molecules also affect the magnitudes of the dispersion forces between them. For example, boiling points for the isomers <em data-effect=\"italics\">n<\/em>-pentane, isopentane, and neopentane (shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_PentIso\">(Figure)<\/a>) are 36 \u00b0C, 27 \u00b0C, and 9.5 \u00b0C, respectively. Even though these compounds are composed of molecules with the same chemical formula, C<sub>5<\/sub>H<sub>12<\/sub>, the difference in boiling points suggests that dispersion forces in the liquid phase are different, being greatest for <em data-effect=\"italics\">n<\/em>-pentane and least for neopentane. The elongated shape of <em data-effect=\"italics\">n<\/em>-pentane provides a greater surface area available for contact between molecules, resulting in correspondingly stronger dispersion forces. The more compact shape of isopentane offers a smaller surface area available for intermolecular contact and, therefore, weaker dispersion forces. Neopentane molecules are the most compact of the three, offering the least available surface area for intermolecular contact and, hence, the weakest dispersion forces. This behavior is analogous to the connections that may be formed between strips of VELCRO brand fasteners: the greater the area of the strip\u2019s contact, the stronger the connection.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_PentIso\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">The strength of the dispersion forces increases with the contact area between molecules, as demonstrated by the boiling points of these pentane isomers.<\/div>\r\n<span id=\"fs-idm29590512\" data-type=\"media\" data-alt=\"Three images of molecules are shown. The first shows a cluster of large, gray spheres each bonded together and to several smaller, white spheres. There is a gray, jagged line and then the mirror image of the first cluster of spheres is shown. Above these two clusters is the label, \u201cSmall contact area, weakest attraction,\u201d and below is the label, \u201cneopentane boiling point: 9.5 degrees C.\u201d The second shows a chain of three gray spheres bonded by the middle sphere to a fourth gray sphere. Each gray sphere is bonded to several smaller, white spheres. There is a jagged, gray line and then the mirror image of the first chain appears. Above these two chains is the label, \u201cLess surface area, less attraction,\u201d and below is the label, \u201cisopentane boiling point: 27 degrees C.\u201d The third image shows a chain of five gray spheres bonded together and to several smaller, white spheres. There is a jagged gray line and then the mirror image of the first chain appears. Above these chains is the label, \u201cLarge contact area, strong attraction,\u201d and below is the label, \u201cn-pentane boiling point 36 degrees C.\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_PentIso-1.jpg\" alt=\"Three images of molecules are shown. The first shows a cluster of large, gray spheres each bonded together and to several smaller, white spheres. There is a gray, jagged line and then the mirror image of the first cluster of spheres is shown. Above these two clusters is the label, \u201cSmall contact area, weakest attraction,\u201d and below is the label, \u201cneopentane boiling point: 9.5 degrees C.\u201d The second shows a chain of three gray spheres bonded by the middle sphere to a fourth gray sphere. Each gray sphere is bonded to several smaller, white spheres. There is a jagged, gray line and then the mirror image of the first chain appears. Above these two chains is the label, \u201cLess surface area, less attraction,\u201d and below is the label, \u201cisopentane boiling point: 27 degrees C.\u201d The third image shows a chain of five gray spheres bonded together and to several smaller, white spheres. There is a jagged gray line and then the mirror image of the first chain appears. Above these chains is the label, \u201cLarge contact area, strong attraction,\u201d and below is the label, \u201cn-pentane boiling point 36 degrees C.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<div id=\"fs-idp29280240\" class=\"chemistry everyday-life\" data-type=\"note\">\r\n<div data-type=\"title\"><\/div>\r\n<div data-type=\"title\"><\/div>\r\n<div data-type=\"title\"><strong>Geckos and Intermolecular Forces<\/strong><\/div>\r\n<p id=\"fs-idm15049248\">Geckos have an amazing ability to adhere to most surfaces. They can quickly run up smooth walls and across ceilings that have no toe-holds, and they do this without having suction cups or a sticky substance on their toes. And while a gecko can lift its feet easily as it walks along a surface, if you attempt to pick it up, it sticks to the surface. How are geckos (as well as spiders and some other insects) able to do this? Although this phenomenon has been investigated for hundreds of years, scientists only recently uncovered the details of the process that allows geckos\u2019 feet to behave this way.<\/p>\r\n<p id=\"fs-idp29466368\">Geckos\u2019 toes are covered with hundreds of thousands of tiny hairs known as <em data-effect=\"italics\">setae<\/em>, with each seta, in turn, branching into hundreds of tiny, flat, triangular tips called <em data-effect=\"italics\">spatulae<\/em>. The huge numbers of spatulae on its setae provide a gecko, shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_Geckos\">(Figure)<\/a>, with a large total surface area for sticking to a surface. In 2000, Kellar <span class=\"no-emphasis\" data-type=\"term\">Autumn<\/span>, who leads a multi-institutional gecko research team, found that geckos adhered equally well to both polar silicon dioxide and nonpolar gallium arsenide. This proved that geckos stick to surfaces because of dispersion forces\u2014weak intermolecular attractions arising from temporary, synchronized charge distributions between adjacent molecules. Although dispersion forces are very weak, the total attraction over millions of spatulae is large enough to support many times the gecko\u2019s weight.<\/p>\r\n<p id=\"fs-idm74321904\">In 2014, two scientists developed a model to explain how geckos can rapidly transition from \u201csticky\u201d to \u201cnon-sticky.\u201d Alex <span class=\"no-emphasis\" data-type=\"term\">Greaney<\/span> and Congcong <span class=\"no-emphasis\" data-type=\"term\">Hu<\/span> at Oregon State University described how geckos can achieve this by changing the angle between their spatulae and the surface. Geckos\u2019 feet, which are normally nonsticky, become sticky when a small shear force is applied. By curling and uncurling their toes, geckos can alternate between sticking and unsticking from a surface, and thus easily move across it. Further investigations may eventually lead to the development of better adhesives and other applications.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_Geckos\" class=\"bc-figure figure\">\r\n<div class=\"bc-figcaption figcaption\">Geckos\u2019 toes contain large numbers of tiny hairs (setae), which branch into many triangular tips (spatulae). Geckos adhere to surfaces because of van der Waals attractions between the surface and a gecko\u2019s millions of spatulae. By changing how the spatulae contact the surface, geckos can turn their stickiness \u201con\u201d and \u201coff.\u201d (credit photo: modification of work by \u201cJC*+A!\u201d\/Flickr)<\/div>\r\n<span id=\"fs-idp79180464\" data-type=\"media\" data-alt=\"Three figures are shown. The first is a photo of the bottom of a gecko\u2019s foot. The second is bigger version which shows the setae. The third is a bigger version of the setae and shows the spatulae.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_Geckos-1.jpg\" alt=\"Three figures are shown. The first is a photo of the bottom of a gecko\u2019s foot. The second is bigger version which shows the setae. The third is a bigger version of the setae and shows the spatulae.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idp133005728\" class=\"chemistry link-to-learning\" data-type=\"note\">\r\n<p id=\"fs-idm71587872\">Watch this <a href=\"http:\/\/openstaxcollege.org\/l\/16kellaraut\">video<\/a> to learn more about Kellar Autumn\u2019s research that determined that van der Waals forces are responsible for a gecko\u2019s ability to cling and climb.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idp3278832\" class=\"bc-section section\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><strong>Dipole-Dipole Attractions<\/strong><\/h3>\r\n<p id=\"fs-idm25328160\">Recall from the chapter on chemical bonding and molecular geometry that <em data-effect=\"italics\">polar<\/em> molecules have a partial positive charge on one side and a partial negative charge on the other side of the molecule\u2014a separation of charge called a <em data-effect=\"italics\">dipole<\/em>. Consider a polar molecule such as hydrogen chloride, HCl. In the HCl molecule, the more electronegative Cl atom bears the partial negative charge, whereas the less electronegative H atom bears the partial positive charge. An attractive force between HCl molecules results from the attraction between the positive end of one HCl molecule and the negative end of another. This attractive force is called a <strong>dipole-dipole attraction<\/strong>\u2014the electrostatic force between the partially positive end of one polar molecule and the partially negative end of another, as illustrated in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_DipDip\">(Figure)<\/a>.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_DipDip\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">This image shows two arrangements of polar molecules, such as HCl, that allow an attraction between the partial negative end of one molecule and the partial positive end of another.<\/div>\r\n<span id=\"fs-idp12575856\" data-type=\"media\" data-alt=\"Two pairs of molecules are shown where each molecule has one larger blue side labeled \u201cdelta sign, negative sign\u201d and a smaller red side labeled \u201cdelta sign, positive sign. In the first pair, the red sides of the two molecules both face to the left and the blue side to the right. A horizontal dotted line lies in between the two. In the second pair, the molecules face up and down, with the red and blue ends aligning. A horizontal dotted line lies between the red and blue ends facing upward and another lies between the red and blue ends facing downward.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_DipDip-1.jpg\" alt=\"Two pairs of molecules are shown where each molecule has one larger blue side labeled \u201cdelta sign, negative sign\u201d and a smaller red side labeled \u201cdelta sign, positive sign. In the first pair, the red sides of the two molecules both face to the left and the blue side to the right. A horizontal dotted line lies in between the two. In the second pair, the molecules face up and down, with the red and blue ends aligning. A horizontal dotted line lies between the red and blue ends facing upward and another lies between the red and blue ends facing downward.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idp108426992\">The effect of a dipole-dipole attraction is apparent when we compare the properties of HCl molecules to nonpolar F<sub>2<\/sub> molecules. Both HCl and F<sub>2<\/sub> consist of the same number of atoms and have approximately the same molecular mass. At a temperature of 150 K, molecules of both substances would have the same average KE. However, the dipole-dipole attractions between HCl molecules are sufficient to cause them to \u201cstick together\u201d to form a liquid, whereas the relatively weaker dispersion forces between nonpolar F<sub>2<\/sub> molecules are not, and so this substance is gaseous at this temperature. The higher normal boiling point of HCl (188 K) compared to F<sub>2<\/sub> (85 K) is a reflection of the greater strength of dipole-dipole attractions between HCl molecules, compared to the attractions between nonpolar F<sub>2<\/sub> molecules. We will often use values such as boiling or freezing points, or enthalpies of vaporization or fusion, as indicators of the relative strengths of IMFs of attraction present within different substances.<\/p>\r\n\r\n<div id=\"fs-idm116129040\" class=\"textbox textbox--examples\" data-type=\"example\">\r\n<p id=\"fs-idm21276784\"><strong>Dipole-Dipole Forces and Their Effects:<\/strong><\/p>\r\nPredict which will have the higher boiling point: N<sub>2<\/sub> or CO. Explain your reasoning.\r\n<p id=\"fs-idm69572480\"><strong>Solution:<\/strong><\/p>\r\nCO and N<sub>2<\/sub> are both diatomic molecules with masses of about 28 u, so they experience similar London dispersion forces. Because CO is a polar molecule, it experiences dipole-dipole attractions. Because N<sub>2<\/sub> is nonpolar, its molecules cannot exhibit dipole-dipole attractions. The dipole-dipole attractions between CO molecules are comparably stronger than the dispersion forces between nonpolar N<sub>2<\/sub> molecules, so CO is expected to have the higher boiling point.\r\n\r\n&nbsp;\r\n<p id=\"fs-idp56618608\"><strong>Check Your Learning:<\/strong><\/p>\r\nPredict which will have the higher boiling point: ICl or Br<sub>2<\/sub>. Explain your reasoning.\r\n\r\n&nbsp;\r\n<div id=\"fs-idm21037552\" data-type=\"note\">\r\n<div data-type=\"title\"><strong>Answer:<\/strong><\/div>\r\n<p id=\"fs-idp57843568\">ICl. ICl and Br<sub>2<\/sub> have similar masses (~160 u) and therefore experience similar London dispersion forces. ICl is polar and thus also exhibits dipole-dipole attractions; Br<sub>2<\/sub> is nonpolar and does not. The relatively stronger dipole-dipole attractions require more energy to overcome, so ICl will have the higher boiling point.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idp42198272\" class=\"bc-section section\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><strong>Hydrogen Bonding<\/strong><\/h3>\r\n<p id=\"fs-idp18167328\">Nitrosyl fluoride (ONF, molecular mass 49 u) is a gas at room temperature. Water (H<sub>2<\/sub>O, molecular mass 18 u) is a liquid, even though it has a lower molecular mass. We clearly cannot attribute this difference between the two compounds to dispersion forces. Both molecules have about the same shape and ONF is the heavier and larger molecule. It is, therefore, expected to experience more significant dispersion forces. Additionally, we cannot attribute this difference in boiling points to differences in the dipole moments of the molecules. Both molecules are polar and exhibit comparable dipole moments. The large difference between the boiling points is due to a particularly strong dipole-dipole attraction that may occur when a molecule contains a hydrogen atom bonded to a fluorine, oxygen, or nitrogen atom (the three most electronegative elements). The very large difference in electronegativity between the H atom (2.1) and the atom to which it is bonded (4.0 for an F atom, 3.5 for an O atom, or 3.0 for a N atom), combined with the very small size of a H atom and the relatively small sizes of F, O, or N atoms, leads to <em data-effect=\"italics\">highly concentrated partial charges<\/em> with these atoms. Molecules with F-H, O-H, or N-H moieties are very strongly attracted to similar moieties in nearby molecules, a particularly strong type of dipole-dipole attraction called <strong>hydrogen bonding<\/strong>. Examples of hydrogen bonds include HF\u22efHF, H<sub>2<\/sub>O\u22efHOH, and H<sub>3<\/sub>N\u22efHNH<sub>2<\/sub>, in which the hydrogen bonds are denoted by dots. <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_HBonding\">(Figure)<\/a> illustrates hydrogen bonding between water molecules.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_HBonding\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">Water molecules participate in multiple hydrogen-bonding interactions with nearby water molecules.<\/div>\r\n<span id=\"fs-idp29073168\" data-type=\"media\" data-alt=\"Five water molecules are shown near one another, but not touching. A dotted line lies between many of the hydrogen atoms on one molecule and the oxygen atom on another molecule.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_HBonding-1.jpg\" alt=\"Five water molecules are shown near one another, but not touching. A dotted line lies between many of the hydrogen atoms on one molecule and the oxygen atom on another molecule.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idp128658848\">Despite use of the word \u201cbond,\u201d keep in mind that hydrogen bonds are <em data-effect=\"italics\">intermolecular<\/em> attractive forces, not <em data-effect=\"italics\">intramolecular<\/em> attractive forces (covalent bonds). Hydrogen bonds are much weaker than covalent bonds, only about 5 to 10% as strong, but are generally much stronger than other dipole-dipole attractions and dispersion forces.<\/p>\r\n<p id=\"fs-idp20088928\">Hydrogen bonds have a pronounced effect on the properties of condensed phases (liquids and solids). For example, consider the trends in boiling points for the binary hydrides of group 15 (NH<sub>3<\/sub>, PH<sub>3<\/sub>, AsH<sub>3<\/sub>, and SbH<sub>3<\/sub>), group 16 hydrides (H<sub>2<\/sub>O, H<sub>2<\/sub>S, H<sub>2<\/sub>Se, and H<sub>2<\/sub>Te), and group 17 hydrides (HF, HCl, HBr, and HI). The boiling points of the heaviest three hydrides for each group are plotted in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_HydrideBP1\">(Figure)<\/a>. As we progress down any of these groups, the polarities of the molecules decrease slightly, whereas the sizes of the molecules increase substantially. The effect of increasingly stronger dispersion forces dominates that of increasingly weaker dipole-dipole attractions, and the boiling points are observed to increase steadily.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_HydrideBP1\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">For the group 15, 16, and 17 hydrides, the boiling points for each class of compounds increase with increasing molecular mass for elements in periods 3, 4, and 5.<\/div>\r\n<span id=\"fs-idm21286928\" data-type=\"media\" data-alt=\"A line graph is shown where the y-axis is labeled \u201cBoiling point (, degree sign, C )\u201d and has values of \u201c negative 150\u201d to \u201c150\u201d from bottom to top in increments of 50. The x-axis is labeled \u201cPeriod\u201d and has values of \u201c0\u201d to \u201c5\u201d in increments of 1. Three lines are shown on the graph and are labeled in the legend. The red line is labeled as \u201chalogen family,\u201d the blue is \u201coxygen family\u201d and the green is \u201cnitrogen family.\u201d The first point on the red line is labeled \u201cquestion mark\u201d and is at point \u201c2, negative 120\u201d. The second point on the line is labeled \u201cH C l\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cH B r\u201d and is at point \u201c4, negative 60\u201d. The fourth point on the line is labeled \u201cH I\u201d and is at point \u201c5, negative 40.\u201d The first point on the green line is labeled \u201cquestion mark\u201d and is at point \u201c2, negative 125.\u201d The second point on the line is labeled \u201cP H, subscript 3\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cA s H, subscript 3\u201d and is at point \u201c4, negative 55.\u201d The fourth point on the line is labeled \u201cS b H, subscript 3\u201d and is at point \u201c5, negative 10.\u201d The first point on the blue line is labeled \u201cquestion mark\u201d and is at point \u201c2, negative 80.\u201d The second point on the line is labeled \u201cH, subscript 2, S\u201d and is at point \u201c3, negative 55\u201d while the third point on the line is labeled \u201cH, subscript 2, S e\u201d and is at point \u201c4, negative 45.\u201d The fourth point on the line is labeled \u201cH, subscript 2, T e\u201d and is at point \u201c5, negative 3.\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_HydrideBP1-1.jpg\" alt=\"A line graph is shown where the y-axis is labeled \u201cBoiling point (, degree sign, C )\u201d and has values of \u201c negative 150\u201d to \u201c150\u201d from bottom to top in increments of 50. The x-axis is labeled \u201cPeriod\u201d and has values of \u201c0\u201d to \u201c5\u201d in increments of 1. Three lines are shown on the graph and are labeled in the legend. The red line is labeled as \u201chalogen family,\u201d the blue is \u201coxygen family\u201d and the green is \u201cnitrogen family.\u201d The first point on the red line is labeled \u201cquestion mark\u201d and is at point \u201c2, negative 120\u201d. The second point on the line is labeled \u201cH C l\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cH B r\u201d and is at point \u201c4, negative 60\u201d. The fourth point on the line is labeled \u201cH I\u201d and is at point \u201c5, negative 40.\u201d The first point on the green line is labeled \u201cquestion mark\u201d and is at point \u201c2, negative 125.\u201d The second point on the line is labeled \u201cP H, subscript 3\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cA s H, subscript 3\u201d and is at point \u201c4, negative 55.\u201d The fourth point on the line is labeled \u201cS b H, subscript 3\u201d and is at point \u201c5, negative 10.\u201d The first point on the blue line is labeled \u201cquestion mark\u201d and is at point \u201c2, negative 80.\u201d The second point on the line is labeled \u201cH, subscript 2, S\u201d and is at point \u201c3, negative 55\u201d while the third point on the line is labeled \u201cH, subscript 2, S e\u201d and is at point \u201c4, negative 45.\u201d The fourth point on the line is labeled \u201cH, subscript 2, T e\u201d and is at point \u201c5, negative 3.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idp26510624\">If we use this trend to predict the boiling points for the lightest hydride for each group, we would expect NH<sub>3<\/sub> to boil at about \u2212120 \u00b0C, H<sub>2<\/sub>O to boil at about \u221280 \u00b0C, and HF to boil at about \u2212110 \u00b0C. However, when we measure the boiling points for these compounds, we find that they are dramatically higher than the trends would predict, as shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_HydrideBP2\">(Figure)<\/a>. The stark contrast between our na\u00efve predictions and reality provides compelling evidence for the strength of hydrogen bonding.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_HydrideBP2\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">In comparison to periods 3\u22125, the binary hydrides of period 2 elements in groups 17, 16 and 15 (F, O and N, respectively) exhibit anomalously high boiling points due to hydrogen bonding.<\/div>\r\n<span id=\"fs-idp79204320\" data-type=\"media\" data-alt=\"A line graph is shown where the y-axis is labeled \u201cBoiling point, ( degree sign, C )\u201d and has values of \u201cnegative 150\u201d to \u201c150\u201d from bottom to top in increments of 50. The x-axis is labeled \u201cPeriod\u201d and has values of \u201c0\u201d to \u201c5\u201d in increments of 1. Three lines are shown on the graph and are labeled in the legend. The red line is labeled as \u201chalogen family,\u201d the blue is \u201coxygen family\u201d and the green is \u201cnitrogen family.\u201d The first point on the red line is labeled \u201cH F\u201d and is at point \u201c2, 25.\u201d The second point on the line is labeled \u201cH C l\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cH B r\u201d and is at point \u201c4, negative 60.\u201d The fourth point on the line is labeled \u201cH I\u201d and is at point \u201c5, negative 40.\u201d The first point on the green line is labeled \u201cN H, subscript 3\u201d and is at point \u201c2, negative 40.\u201d The second point on the line is labeled \u201cP H, subscript 3\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cA s H, subscript 3\u201d and is at point \u201c4, negative 55.\u201d The fourth point on the line is labeled \u201cS b H, subscript 3\u201d and is at point \u201c5, negative 10.\u201d The first point on the blue line is labeled \u201cH, subscript 2, O\u201d and is at point \u201c2, 100.\u201d The second point on the line is labeled \u201cH, subscript 2, S\u201d and is at point \u201c3, negative 55\u201d while the third point on the line is labeled \u201cH, subscript 2, S e\u201d and is at point \u201c4, negative 45.\u201d The fourth point on the line is labeled \u201cH, subscript 2, T e\u201d and is at point \u201c5, negative 3.\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_HydrideBP2-1.jpg\" alt=\"A line graph is shown where the y-axis is labeled \u201cBoiling point, ( degree sign, C )\u201d and has values of \u201cnegative 150\u201d to \u201c150\u201d from bottom to top in increments of 50. The x-axis is labeled \u201cPeriod\u201d and has values of \u201c0\u201d to \u201c5\u201d in increments of 1. Three lines are shown on the graph and are labeled in the legend. The red line is labeled as \u201chalogen family,\u201d the blue is \u201coxygen family\u201d and the green is \u201cnitrogen family.\u201d The first point on the red line is labeled \u201cH F\u201d and is at point \u201c2, 25.\u201d The second point on the line is labeled \u201cH C l\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cH B r\u201d and is at point \u201c4, negative 60.\u201d The fourth point on the line is labeled \u201cH I\u201d and is at point \u201c5, negative 40.\u201d The first point on the green line is labeled \u201cN H, subscript 3\u201d and is at point \u201c2, negative 40.\u201d The second point on the line is labeled \u201cP H, subscript 3\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cA s H, subscript 3\u201d and is at point \u201c4, negative 55.\u201d The fourth point on the line is labeled \u201cS b H, subscript 3\u201d and is at point \u201c5, negative 10.\u201d The first point on the blue line is labeled \u201cH, subscript 2, O\u201d and is at point \u201c2, 100.\u201d The second point on the line is labeled \u201cH, subscript 2, S\u201d and is at point \u201c3, negative 55\u201d while the third point on the line is labeled \u201cH, subscript 2, S e\u201d and is at point \u201c4, negative 45.\u201d The fourth point on the line is labeled \u201cH, subscript 2, T e\u201d and is at point \u201c5, negative 3.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<div id=\"fs-idm118983568\" class=\"textbox textbox--examples\" data-type=\"example\">\r\n<p id=\"fs-idp138845584\"><strong>Effect of Hydrogen Bonding on Boiling Points:<\/strong><\/p>\r\nConsider the compounds dimethylether (CH<sub>3<\/sub>OCH<sub>3<\/sub>), ethanol (CH<sub>3<\/sub>CH<sub>2<\/sub>OH), and propane (CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>3<\/sub>). Their boiling points, not necessarily in order, are \u221242.1 \u00b0C, \u221224.8 \u00b0C, and 78.4 \u00b0C. Match each compound with its boiling point. Explain your reasoning.\r\n\r\n&nbsp;\r\n<p id=\"fs-idm50766656\"><strong>Solution:<\/strong><\/p>\r\nThe VSEPR-predicted shapes of CH<sub>3<\/sub>OCH<sub>3<\/sub>, CH<sub>3<\/sub>CH<sub>2<\/sub>OH, and CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>3<\/sub> are similar, as are their molar masses (46 g\/mol, 46 g\/mol, and 44 g\/mol, respectively), so they will exhibit similar dispersion forces. Since CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>3<\/sub> is nonpolar, it may exhibit <em data-effect=\"italics\">only<\/em> dispersion forces. Because CH<sub>3<\/sub>OCH<sub>3<\/sub> is polar, it will also experience dipole-dipole attractions. Finally, CH<sub>3<\/sub>CH<sub>2<\/sub>OH has an \u2212OH group, and so it will experience the uniquely strong dipole-dipole attraction known as hydrogen bonding. So the ordering in terms of strength of IMFs, and thus boiling points, is CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>3<\/sub> &lt; CH<sub>3<\/sub>OCH<sub>3<\/sub> &lt; CH<sub>3<\/sub>CH<sub>2<\/sub>OH. The boiling point of propane is \u221242.1 \u00b0C, the boiling point of dimethylether is \u221224.8 \u00b0C, and the boiling point of ethanol is 78.5 \u00b0C.\r\n\r\n&nbsp;\r\n<p id=\"fs-idm47706096\"><strong>Check Your Learning:<\/strong><\/p>\r\nEthane (CH<sub>3<\/sub>CH<sub>3<\/sub>) has a melting point of \u2212183 \u00b0C and a boiling point of \u221289 \u00b0C. Predict the melting and boiling points for methylamine (CH<sub>3<\/sub>NH<sub>2<\/sub>). Explain your reasoning.\r\n\r\n&nbsp;\r\n<div id=\"fs-idm67186592\" data-type=\"note\">\r\n<div data-type=\"title\"><strong>Answer:<\/strong><\/div>\r\n<p id=\"fs-idm91556848\">The melting point and boiling point for methylamine are predicted to be significantly greater than those of ethane. CH<sub>3<\/sub>CH<sub>3<\/sub> and CH<sub>3<\/sub>NH<sub>2<\/sub> are similar in size and mass, but methylamine possesses an \u2212NH group and therefore may exhibit hydrogen bonding. This greatly increases its IMFs, and therefore its melting and boiling points. It is difficult to predict values, but the known values are a melting point of \u221293 \u00b0C and a boiling point of \u22126 \u00b0C.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm44601856\" class=\"chemistry sciences-interconnect\" data-type=\"note\">\r\n<div data-type=\"title\"><\/div>\r\n<div data-type=\"title\"><strong>Hydrogen Bonding and DNA<\/strong><\/div>\r\n<p id=\"fs-idm79852624\">Deoxyribonucleic acid (DNA) is found in every living organism and contains the genetic information that determines the organism\u2019s characteristics, provides the blueprint for making the proteins necessary for life, and serves as a template to pass this information on to the organism\u2019s offspring. A DNA molecule consists of two (anti-)parallel chains of repeating nucleotides, which form its well-known double helical structure, as shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_DNA\">(Figure)<\/a>.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_DNA\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">Two separate DNA molecules form a double-stranded helix in which the molecules are held together via hydrogen bonding. (credit: modification of work by Jerome Walker, Dennis Myts)<\/div>\r\n<span id=\"fs-idm97606608\" data-type=\"media\" data-alt=\"Two images are shown. The first lies on the left side of the page and shows a helical structure like a twisted ladder where the rungs of the ladder, labeled \u201cBase pair\u201d are red, yellow, green and blue paired bars. The red and yellow bars, which are always paired together, are labeled in the legend, which is titled \u201cNitrogenous bases\u201d as \u201cadenine\u201d and \u201cthymine,\u201d respectively. The blue and green bars, which are always paired together, are labeled in the legend as \u201cguanine\u201d and \u201ccytosine,\u201d respectively. At the top of the helical structure, the left-hand side rail, or \u201cSugar, dash, phosphate backbone,\u201d is labeled as \u201c3, prime\u201d while the right is labeled as \u201c5, prime.\u201d These labels are reversed at the bottom of the helix. To the right of the page is a large Lewis structure. The top left corner of this structure, labeled \u201c5, prime,\u201d shows a phosphorus atom single bonded to three oxygen atoms, one of which has a superscripted negative charge, and double bonded to a fourth oxygen atom. One of the single bonded oxygen atoms is single bonded to the left corner of a five-membered ring with an oxygen atom at its top point and which is single bonded to an oxygen atom on the bottom left. This oxygen atom is single bonded to a phosphorus atom that is single bonded to two other hydrogen atoms and double bonded to a fourth oxygen atom. The lower left of these oxygen atoms is single bonded to another oxygen atom that is single bonded to a five-membered ring with an oxygen in the upper bonding site. The bottom left of this ring has a hydroxyl group attached to it while the upper right carbon is single bonded to a nitrogen atom that is part of a five-membered ring bonded to a six-membered ring. Both of these rings have points of unsaturation and nitrogen atoms bonded into their structures. On the right side of the six-membered ring are two single bonded amine groups and a double bonded oxygen. Three separate dotted lines extend from these sites to corresponding sites on a second six-membered ring. This ring has points of unsaturation and a nitrogen atom in the bottom right bonding position that is single bonded to a five-membered ring on the right side of the image. This ring is single bonded to a carbon that is single bonded to an oxygen that is single bonded to a phosphorus. The phosphorus is single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. This group is labeled \u201c5, prime.\u201d The five-membered ring is also bonded on the top side to an oxygen that is bonded to a phosphorus single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. The upper left oxygen of this group is single bonded to a carbon that is single bonded to a five-membered ring with an oxygen in the bottom bonding position. This ring has a hydroxyl group on its upper right side that is labeled \u201c3, prime\u201d and is bonded on the left side to a nitrogen that is a member of a five-membered ring. This ring is bonded to a six-membered ring and both have points of unsaturation. This ring has a nitrogen on the left side, as well as an amine group, that have two dotted lines leading from them to an oxygen and amine group on a six membered ring. These dotted lines are labeled \u201cHydrogen bonds.\u201d The six membered ring also has a double bonded oxygen on its lower side and a nitrogen atom on its left side that is single bonded to a five-membered ring. This ring connects to the two phosphate groups mentioned at the start of this to form a large circle. The name \u201cguanine\u201d is written below the lower left side of this image while the name \u201ccytosine\u201d is written on the lower right. The name \u201cthymine\u201d is written above the right side of the image and \u201cadenine\u201d is written on the top right. Three sections are indicated below the images where the left is labeled \u201cSugar, dash, phosphate backbone,\u201d the middle is labeled \u201cBases\u201d and the right is labeled \u201cSugar, dash, phosphate backbone.\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_DNA-1.jpg\" alt=\"Two images are shown. The first lies on the left side of the page and shows a helical structure like a twisted ladder where the rungs of the ladder, labeled \u201cBase pair\u201d are red, yellow, green and blue paired bars. The red and yellow bars, which are always paired together, are labeled in the legend, which is titled \u201cNitrogenous bases\u201d as \u201cadenine\u201d and \u201cthymine,\u201d respectively. The blue and green bars, which are always paired together, are labeled in the legend as \u201cguanine\u201d and \u201ccytosine,\u201d respectively. At the top of the helical structure, the left-hand side rail, or \u201cSugar, dash, phosphate backbone,\u201d is labeled as \u201c3, prime\u201d while the right is labeled as \u201c5, prime.\u201d These labels are reversed at the bottom of the helix. To the right of the page is a large Lewis structure. The top left corner of this structure, labeled \u201c5, prime,\u201d shows a phosphorus atom single bonded to three oxygen atoms, one of which has a superscripted negative charge, and double bonded to a fourth oxygen atom. One of the single bonded oxygen atoms is single bonded to the left corner of a five-membered ring with an oxygen atom at its top point and which is single bonded to an oxygen atom on the bottom left. This oxygen atom is single bonded to a phosphorus atom that is single bonded to two other hydrogen atoms and double bonded to a fourth oxygen atom. The lower left of these oxygen atoms is single bonded to another oxygen atom that is single bonded to a five-membered ring with an oxygen in the upper bonding site. The bottom left of this ring has a hydroxyl group attached to it while the upper right carbon is single bonded to a nitrogen atom that is part of a five-membered ring bonded to a six-membered ring. Both of these rings have points of unsaturation and nitrogen atoms bonded into their structures. On the right side of the six-membered ring are two single bonded amine groups and a double bonded oxygen. Three separate dotted lines extend from these sites to corresponding sites on a second six-membered ring. This ring has points of unsaturation and a nitrogen atom in the bottom right bonding position that is single bonded to a five-membered ring on the right side of the image. This ring is single bonded to a carbon that is single bonded to an oxygen that is single bonded to a phosphorus. The phosphorus is single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. This group is labeled \u201c5, prime.\u201d The five-membered ring is also bonded on the top side to an oxygen that is bonded to a phosphorus single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. The upper left oxygen of this group is single bonded to a carbon that is single bonded to a five-membered ring with an oxygen in the bottom bonding position. This ring has a hydroxyl group on its upper right side that is labeled \u201c3, prime\u201d and is bonded on the left side to a nitrogen that is a member of a five-membered ring. This ring is bonded to a six-membered ring and both have points of unsaturation. This ring has a nitrogen on the left side, as well as an amine group, that have two dotted lines leading from them to an oxygen and amine group on a six membered ring. These dotted lines are labeled \u201cHydrogen bonds.\u201d The six membered ring also has a double bonded oxygen on its lower side and a nitrogen atom on its left side that is single bonded to a five-membered ring. This ring connects to the two phosphate groups mentioned at the start of this to form a large circle. The name \u201cguanine\u201d is written below the lower left side of this image while the name \u201ccytosine\u201d is written on the lower right. The name \u201cthymine\u201d is written above the right side of the image and \u201cadenine\u201d is written on the top right. Three sections are indicated below the images where the left is labeled \u201cSugar, dash, phosphate backbone,\u201d the middle is labeled \u201cBases\u201d and the right is labeled \u201cSugar, dash, phosphate backbone.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idp113560512\">Each nucleotide contains a (deoxyribose) sugar bound to a phosphate group on one side, and one of four nitrogenous bases on the other. Two of the bases, cytosine (C) and thymine (T), are single-ringed structures known as pyrimidines. The other two, adenine (A) and guanine (G), are double-ringed structures called purines. These bases form complementary base pairs consisting of one purine and one pyrimidine, with adenine pairing with thymine, and cytosine with guanine. Each base pair is held together by hydrogen bonding. A and T share two hydrogen bonds, C and G share three, and both pairings have a similar shape and structure <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_DNA2\">(Figure)<\/a>.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_10_01_DNA2\" class=\"bc-figure figure\">\r\n<div class=\"bc-figcaption figcaption\">The geometries of the base molecules result in maximum hydrogen bonding between adenine and thymine (AT) and between guanine and cytosine (GC), so-called \u201ccomplementary base pairs.\u201d<\/div>\r\n<span id=\"fs-idm64449536\" data-type=\"media\" data-alt=\"A large Lewis structure is shown. The top left corner of this structure, labeled \u201c5, prime,\u201d shows a phosphorus atom single bonded to three oxygen atoms, one of which has a superscripted negative charge, and double bonded to a fourth oxygen atom. One of the single bonded oxygen atoms is single bonded to the left corner of a five-membered ring with an oxygen atom at its top point and which is single bonded to an oxygen atom on the bottom left. This oxygen atom is single bonded to a phosphorus atom that is single bonded to two other hydrogen atoms and double bonded to a fourth oxygen atom. The lower left of these oxygen atoms is single bonded to another oxygen atom that is single bonded to a five-membered ring with an oxygen in the upper bonding site. The bottom left of this ring has a hydroxyl group attached to it while the upper right carbon is single bonded to a nitrogen atom that is part of a five-membered ring bonded to a six-membered ring. Both of these rings have points of unsaturation and nitrogen atoms bonded into their structures. On the right side of the six-membered ring are two single bonded amine groups and a double bonded oxygen. Three separate dotted lines extend from these sites to corresponding sites on a second six-membered ring. This ring has points of unsaturation and a nitrogen atom in the bottom right bonding position that is single bonded to a five-membered ring on the right side of the image. This ring is single bonded to a carbon that is single bonded to an oxygen that is single bonded to a phosphorus. The phosphorus is single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. This group is labeled \u201c5, prime.\u201d The five-membered ring is also bonded on the top side to an oxygen that is bonded to a phosphorus single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. The upper left oxygen of this group is single bonded to a carbon that is single bonded to a five-membered ring with an oxygen in the bottom bonding position. This ring has a hydroxyl group on its upper right side that is labeled \u201c3, prime\u201d and is bonded on the left side to a nitrogen that is a member of a five-membered ring. This ring is bonded to a six-membered ring and both have points of unsaturation. This ring has a nitrogen on the left side, as well as an amine group, that have two dotted lines leading from them to an oxygen and amine group on a six membered ring. These dotted lines are labeled \u201cHydrogen bonds.\u201d The six membered ring also has a double bonded oxygen on its lower side and a nitrogen atom on its left side that is single bonded to a five-membered ring. This ring connects to the two phosphate groups mentioned at the start of this to form a large circle. The name \u201cguanine\u201d is written below the lower left side of this image while the name \u201ccytosine\u201d is written on the lower right. The name \u201cthymine\u201d is written above the right side of the image and \u201cadenine\u201d is written on the top right. Three sections are indicated below the images where the left is labeled \u201cSugar, dash, phosphate backbone,\u201d the middle is labeled \u201cBases\u201d and the right is labeled \u201cSugar, dash, phosphate backbone.\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_DNA2-1.jpg\" alt=\"A large Lewis structure is shown. The top left corner of this structure, labeled \u201c5, prime,\u201d shows a phosphorus atom single bonded to three oxygen atoms, one of which has a superscripted negative charge, and double bonded to a fourth oxygen atom. One of the single bonded oxygen atoms is single bonded to the left corner of a five-membered ring with an oxygen atom at its top point and which is single bonded to an oxygen atom on the bottom left. This oxygen atom is single bonded to a phosphorus atom that is single bonded to two other hydrogen atoms and double bonded to a fourth oxygen atom. The lower left of these oxygen atoms is single bonded to another oxygen atom that is single bonded to a five-membered ring with an oxygen in the upper bonding site. The bottom left of this ring has a hydroxyl group attached to it while the upper right carbon is single bonded to a nitrogen atom that is part of a five-membered ring bonded to a six-membered ring. Both of these rings have points of unsaturation and nitrogen atoms bonded into their structures. On the right side of the six-membered ring are two single bonded amine groups and a double bonded oxygen. Three separate dotted lines extend from these sites to corresponding sites on a second six-membered ring. This ring has points of unsaturation and a nitrogen atom in the bottom right bonding position that is single bonded to a five-membered ring on the right side of the image. This ring is single bonded to a carbon that is single bonded to an oxygen that is single bonded to a phosphorus. The phosphorus is single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. This group is labeled \u201c5, prime.\u201d The five-membered ring is also bonded on the top side to an oxygen that is bonded to a phosphorus single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. The upper left oxygen of this group is single bonded to a carbon that is single bonded to a five-membered ring with an oxygen in the bottom bonding position. This ring has a hydroxyl group on its upper right side that is labeled \u201c3, prime\u201d and is bonded on the left side to a nitrogen that is a member of a five-membered ring. This ring is bonded to a six-membered ring and both have points of unsaturation. This ring has a nitrogen on the left side, as well as an amine group, that have two dotted lines leading from them to an oxygen and amine group on a six membered ring. These dotted lines are labeled \u201cHydrogen bonds.\u201d The six membered ring also has a double bonded oxygen on its lower side and a nitrogen atom on its left side that is single bonded to a five-membered ring. This ring connects to the two phosphate groups mentioned at the start of this to form a large circle. The name \u201cguanine\u201d is written below the lower left side of this image while the name \u201ccytosine\u201d is written on the lower right. The name \u201cthymine\u201d is written above the right side of the image and \u201cadenine\u201d is written on the top right. Three sections are indicated below the images where the left is labeled \u201cSugar, dash, phosphate backbone,\u201d the middle is labeled \u201cBases\u201d and the right is labeled \u201cSugar, dash, phosphate backbone.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idp108968272\">The cumulative effect of millions of hydrogen bonds effectively holds the two strands of DNA together. Importantly, the two strands of DNA can relatively easily \u201cunzip\u201d down the middle since hydrogen bonds are relatively weak compared to the covalent bonds that hold the atoms of the individual DNA molecules together. This allows both strands to function as a template for replication.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm78986320\" class=\"summary\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><strong>Key Concepts and Summary<\/strong><\/h3>\r\n<p id=\"fs-idp42400528\">The physical properties of condensed matter (liquids and solids) can be explained in terms of the kinetic molecular theory. In a liquid, intermolecular attractive forces hold the molecules in contact, although they still have sufficient KE to move past each other.<\/p>\r\n<p id=\"fs-idp113514832\">Intermolecular attractive forces, collectively referred to as van der Waals forces, are responsible for the behavior of liquids and solids and are electrostatic in nature. Dipole-dipole attractions result from the electrostatic attraction of the partial negative end of one dipolar molecule for the partial positive end of another. The temporary dipole that results from the motion of the electrons in an atom can induce a dipole in an adjacent atom and give rise to the London dispersion force. London forces increase with increasing molecular size. Hydrogen bonds are a special type of dipole-dipole attraction that results when hydrogen is bonded to one of the three most electronegative elements: F, O, or N.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idp29893056\" class=\"exercises\" data-depth=\"1\">\r\n<div id=\"fs-idp70845808\" data-type=\"exercise\">\r\n<div id=\"fs-idm12315280\" data-type=\"problem\"><\/div>\r\n<\/div>\r\n<div id=\"fs-idp18248944\" data-type=\"exercise\">\r\n<div id=\"fs-idp1597760\" data-type=\"solution\">\r\n<p id=\"fs-idm63875504\"><\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox shaded\" data-type=\"glossary\">\r\n<h3 data-type=\"glossary-title\"><strong>Glossary<\/strong><\/h3>\r\n<dl id=\"fs-idp127496336\">\r\n \t<dt>dipole-dipole attraction<\/dt>\r\n \t<dd id=\"fs-idm18049984\">intermolecular attraction between two permanent dipoles<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-idm16566240\">\r\n \t<dt>dispersion force<\/dt>\r\n \t<dd id=\"fs-idm58382832\">(also, London dispersion force) attraction between two rapidly fluctuating, temporary dipoles; significant only when particles are very close together<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-idp18243872\">\r\n \t<dt>hydrogen bonding<\/dt>\r\n \t<dd id=\"fs-idm24342960\">occurs when exceptionally strong dipoles attract; bonding that exists when hydrogen is bonded to one of the three most electronegative elements: F, O, or N<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-idm31438528\">\r\n \t<dt>induced dipole<\/dt>\r\n \t<dd id=\"fs-idm98054496\">temporary dipole formed when the electrons of an atom or molecule are distorted by the instantaneous dipole of a neighboring atom or molecule<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-idp127211536\">\r\n \t<dt>instantaneous dipole<\/dt>\r\n \t<dd id=\"fs-idm23826208\">temporary dipole that occurs for a brief moment in time when the electrons of an atom or molecule are distributed asymmetrically<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-idm66585952\">\r\n \t<dt>intermolecular force<\/dt>\r\n \t<dd id=\"fs-idp135842976\">noncovalent attractive force between atoms, molecules, and\/or ions<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-idp128571888\">\r\n \t<dt>polarizability<\/dt>\r\n \t<dd id=\"fs-idm53459296\">measure of the ability of a charge to distort a molecule\u2019s charge distribution (electron cloud)<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-idm134093104\">\r\n \t<dt>van der Waals force<\/dt>\r\n \t<dd id=\"fs-idm67077760\">attractive or repulsive force between molecules, including dipole-dipole, dipole-induced dipole, and London dispersion forces; does not include forces due to covalent or ionic bonding, or the attraction between ions and molecules<\/dd>\r\n<\/dl>\r\n<\/div>","rendered":"<div class=\"textbox textbox--learning-objectives\">\n<h3><strong>Learning Objectives<\/strong><\/h3>\n<p>By the end of this section, you will be able to:<\/p>\n<ul>\n<li>Describe the types of intermolecular forces possible between atoms or molecules in condensed phases (dispersion forces, dipole-dipole attractions, and hydrogen bonding)<\/li>\n<li>Identify the types of intermolecular forces experienced by specific molecules based on their structures<\/li>\n<li>Explain the relation between the intermolecular forces present within a substance and the temperatures associated with changes in its physical state<\/li>\n<\/ul>\n<\/div>\n<p id=\"fs-idp55691520\">As was the case for gaseous substances, the kinetic molecular theory may be used to explain the behavior of solids and liquids. In the following description, the term <em data-effect=\"italics\">particle<\/em> will be used to refer to an atom, molecule, or ion. Note that we will use the popular phrase \u201cintermolecular attraction\u201d to refer to attractive forces between the particles of a substance, regardless of whether these particles are molecules, atoms, or ions.<\/p>\n<p id=\"fs-idp57413920\">Consider these two aspects of the molecular-level environments in solid, liquid, and gaseous matter:<\/p>\n<ul id=\"fs-idm45003248\" data-bullet-style=\"bullet\">\n<li>Particles in a solid are tightly packed together and often arranged in a regular pattern; in a liquid, they are close together with no regular arrangement; in a gas, they are far apart with no regular arrangement.<\/li>\n<li>Particles in a solid vibrate about fixed positions and do not generally move in relation to one another; in a liquid, they move past each other but remain in essentially constant contact; in a gas, they move independently of one another except when they collide.<\/li>\n<\/ul>\n<p id=\"fs-idm53508384\">The differences in the properties of a solid, liquid, or gas reflect the strengths of the attractive forces between the atoms, molecules, or ions that make up each phase. The phase in which a substance exists depends on the relative extents of its <strong>intermolecular forces (IMFs)<\/strong> and the kinetic energies (KE) of its molecules. IMFs are the various forces of attraction that may exist between the atoms and molecules of a substance due to electrostatic phenomena, as will be detailed in this module. These forces serve to hold particles close together, whereas the particles\u2019 KE provides the energy required to overcome the attractive forces and thus increase the distance between particles. <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_KMTPhases1\">(Figure)<\/a> illustrates how changes in physical state may be induced by changing the temperature, hence, the average KE, of a given substance.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_KMTPhases1\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">Transitions between solid, liquid, and gaseous states of a substance occur when conditions of temperature or pressure favor the associated changes in intermolecular forces. (Note: The space between particles in the gas phase is much greater than shown.)<\/div>\n<p><span id=\"fs-idp1251008\" data-type=\"media\" data-alt=\"Three sealed flasks are labeled, \u201cCrystalline solid,\u201d \u201cLiquid,\u201d and \u201cGas,\u201d from left to right. The first flask holds a cube composed of small spheres sitting on the bottom while the second flask shows a lot of small spheres in the bottom that are spaced a small distance apart from one another and have lines around them to indicate motion. The third flask shows a few spheres spread far from one another with larger lines to indicate motion. There is a right-facing arrow that spans the top of all three flasks. The arrow is labeled, \u201cIncreasing K E ( temperature ).\u201d There is a left-facing arrow that spans the bottom of all three flasks. The arrow is labeled, \u201cIncreasing I M F.\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_KMTPhases1-1.jpg\" alt=\"Three sealed flasks are labeled, \u201cCrystalline solid,\u201d \u201cLiquid,\u201d and \u201cGas,\u201d from left to right. The first flask holds a cube composed of small spheres sitting on the bottom while the second flask shows a lot of small spheres in the bottom that are spaced a small distance apart from one another and have lines around them to indicate motion. The third flask shows a few spheres spread far from one another with larger lines to indicate motion. There is a right-facing arrow that spans the top of all three flasks. The arrow is labeled, \u201cIncreasing K E ( temperature ).\u201d There is a left-facing arrow that spans the bottom of all three flasks. The arrow is labeled, \u201cIncreasing I M F.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idm190830512\">As an example of the processes depicted in this figure, consider a sample of water. When gaseous water is cooled sufficiently, the attractions between H<sub>2<\/sub>O molecules will be capable of holding them together when they come into contact with each other; the gas condenses, forming liquid H<sub>2<\/sub>O. For example, liquid water forms on the outside of a cold glass as the water vapor in the air is cooled by the cold glass, as seen in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_WaterPhase\">(Figure)<\/a>.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_WaterPhase\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">Condensation forms when water vapor in the air is cooled enough to form liquid water, such as (a) on the outside of a cold beverage glass or (b) in the form of fog. (credit a: modification of work by Jenny Downing; credit b: modification of work by Cory Zanker)<\/div>\n<p><span id=\"fs-idp51997104\" data-type=\"media\" data-alt=\"Image a shows a brown colored beverage in a glass with condensation on the outside. Image b shows a body of water with fog hovering above the surface of the water.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_WaterPhase-1.jpg\" alt=\"Image a shows a brown colored beverage in a glass with condensation on the outside. Image b shows a body of water with fog hovering above the surface of the water.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idm59044480\">We can also liquefy many gases by compressing them, if the temperature is not too high. The increased pressure brings the molecules of a gas closer together, such that the attractions between the molecules become strong relative to their KE. Consequently, they form liquids. Butane, C<sub>4<\/sub>H<sub>10<\/sub>, is the fuel used in disposable lighters and is a gas at standard temperature and pressure. Inside the lighter\u2019s fuel compartment, the butane is compressed to a pressure that results in its condensation to the liquid state, as shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_ButanePhase\">(Figure)<\/a>.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_ButanePhase\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">Gaseous butane is compressed within the storage compartment of a disposable lighter, resulting in its condensation to the liquid state. (credit: modification of work by \u201cSam-Cat\u201d\/Flickr)<\/div>\n<p><span id=\"fs-idp136258192\" data-type=\"media\" data-alt=\"A butane lighter is shown.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_ButanePhase-1.jpg\" alt=\"A butane lighter is shown.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idm68544288\">Finally, if the temperature of a liquid becomes sufficiently low, or the pressure on the liquid becomes sufficiently high, the molecules of the liquid no longer have enough KE to overcome the IMF between them, and a solid forms. A more thorough discussion of these and other changes of state, or phase transitions, is provided in a later module of this chapter.<\/p>\n<div id=\"fs-idp144602800\" class=\"chemistry link-to-learning\" data-type=\"note\">\n<p id=\"fs-idp70176880\">Access this <a href=\"http:\/\/openstaxcollege.org\/l\/16phetvisual\">interactive simulation<\/a> on states of matter, phase transitions, and intermolecular forces. This simulation is useful for visualizing concepts introduced throughout this chapter.<\/p>\n<\/div>\n<div id=\"fs-idp48705360\" class=\"bc-section section\" data-depth=\"1\">\n<h3 data-type=\"title\"><strong>Forces between Molecules<\/strong><\/h3>\n<p id=\"fs-idp15601504\">Under appropriate conditions, the attractions between all gas molecules will cause them to form liquids or solids. This is due to intermolecular forces, not <em data-effect=\"italics\">intra<\/em>molecular forces. <em data-effect=\"italics\">Intra<\/em>molecular forces are those <em data-effect=\"italics\">within<\/em> the molecule that keep the molecule together, for example, the bonds between the atoms. <em data-effect=\"italics\">Inter<\/em>molecular forces are the attractions <em data-effect=\"italics\">between<\/em> molecules, which determine many of the physical properties of a substance. <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_IntravInter\">(Figure)<\/a> illustrates these different molecular forces. The strengths of these attractive forces vary widely, though usually the IMFs between small molecules are weak compared to the intramolecular forces that bond atoms together within a molecule. For example, to overcome the IMFs in one mole of liquid HCl and convert it into gaseous HCl requires only about 17 kJ. However, to break the covalent bonds between the hydrogen and chlorine atoms in one mole of HCl requires about 25 times more energy\u2014430 kJ.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_IntravInter\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\"><em data-effect=\"italics\">Intra<\/em>molecular forces keep a molecule intact. <em data-effect=\"italics\">Inter<\/em>molecular forces hold multiple molecules together and determine many of a substance\u2019s properties.<\/div>\n<p><span id=\"fs-idm297424\" data-type=\"media\" data-alt=\"An image is shown in which two molecules composed of a green sphere labeled \u201cC l\u201d connected on the right to a white sphere labeled \u201cH\u201d are near one another with a dotted line labeled \u201cIntermolecular force ( weak )\u201d drawn between them. A line connects the two spheres in each molecule and the line is labeled \u201cIntramolecular force ( strong ).\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_IntravInter-1.jpg\" alt=\"An image is shown in which two molecules composed of a green sphere labeled \u201cC l\u201d connected on the right to a white sphere labeled \u201cH\u201d are near one another with a dotted line labeled \u201cIntermolecular force ( weak )\u201d drawn between them. A line connects the two spheres in each molecule and the line is labeled \u201cIntramolecular force ( strong ).\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idm68677744\">All of the attractive forces between neutral atoms and molecules are known as <span data-type=\"term\">van der Waals forces<\/span>, although they are usually referred to more informally as intermolecular attraction. We will consider the various types of IMFs in the next three sections of this module.<\/p>\n<\/div>\n<div id=\"fs-idm146733840\" class=\"bc-section section\" data-depth=\"1\">\n<h3 data-type=\"title\"><strong>Dispersion Forces<\/strong><\/h3>\n<p id=\"fs-idp26129792\">One of the three van der Waals forces is present in all condensed phases, regardless of the nature of the atoms or molecules composing the substance. This attractive force is called the <strong><span class=\"no-emphasis\" data-type=\"term\">London dispersion force<\/span><\/strong> in honor of German-born American physicist Fritz <span class=\"no-emphasis\" data-type=\"term\">London<\/span> who, in 1928, first explained it. This force is often referred to as simply the <span data-type=\"term\">dispersion force<\/span>. Because the electrons of an atom or molecule are in constant motion (or, alternatively, the electron\u2019s location is subject to quantum-mechanical variability), at any moment in time, an atom or molecule can develop a temporary, <span data-type=\"term\">instantaneous dipole<\/span> if its electrons are distributed asymmetrically. The presence of this dipole can, in turn, distort the electrons of a neighboring atom or molecule, producing an <span data-type=\"term\">induced dipole<\/span>. These two rapidly fluctuating, temporary dipoles thus result in a relatively weak electrostatic attraction between the species\u2014a so-called dispersion force like that illustrated in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_DispForces\">(Figure)<\/a>.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_DispForces\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">Dispersion forces result from the formation of temporary dipoles, as illustrated here for two nonpolar diatomic molecules.<\/div>\n<p><span id=\"fs-idp52348576\" data-type=\"media\" data-alt=\"Two pairs of molecules are shown where each molecule has one larger blue side labeled \u201cdelta sign, negative sign\u201d and a smaller red side labeled \u201cdelta sign, positive sign.\u201d Toward the middle of the both molecules, but still on each distinct side, is a black dot. Between the two images is a dotted line labeled, \u201cAttractive force.\u201d In the first image, the red and blue sides are labeled, \u201cUnequal distribution of electrons.\u201d Below both images are brackets. The brackets are labeled, \u201cTemporary dipoles.\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_DispForces-1.jpg\" alt=\"Two pairs of molecules are shown where each molecule has one larger blue side labeled \u201cdelta sign, negative sign\u201d and a smaller red side labeled \u201cdelta sign, positive sign.\u201d Toward the middle of the both molecules, but still on each distinct side, is a black dot. Between the two images is a dotted line labeled, \u201cAttractive force.\u201d In the first image, the red and blue sides are labeled, \u201cUnequal distribution of electrons.\u201d Below both images are brackets. The brackets are labeled, \u201cTemporary dipoles.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idm80968928\">Dispersion forces that develop between atoms in different molecules can attract the two molecules to each other. The forces are relatively weak, however, and become significant only when the molecules are very close. Larger and heavier atoms and molecules exhibit stronger dispersion forces than do smaller and lighter atoms and molecules. F<sub>2<\/sub> and Cl<sub>2<\/sub> are gases at room temperature (reflecting weaker attractive forces); Br<sub>2<\/sub> is a liquid, and I<sub>2<\/sub> is a solid (reflecting stronger attractive forces). Trends in observed melting and boiling points for the halogens clearly demonstrate this effect, as seen in <a class=\"autogenerated-content\" href=\"#fs-idp55860464\">(Figure)<\/a>.<\/p>\n<table id=\"fs-idp55860464\" class=\"top-titled\" summary=\"This table has six rows and five columns. The first row is a header row and it labels each column: \u201cHalogen,\u201d \u201cMolar Mass,\u201d \u201cAtomic Radius,\u201d \u201cMelting Point,\u201d and \u201cBoiling Point.\u201d Under the \u201cHalogen\u201d column are the following: Fluorine, F subscript 2; Chlorine, C l subscript 2; bromine, B r subscript 2; iodine, I subscript 2; astatine, A t subscript 2. Under the \u201cMolar Mass\u201d column are the following: 38 g \/ mol; 71 g \/ mol; 160 g \/ mol; 254 g \/ mol; 420 g \/ mol. Under the \u201cAtomic Radius\u201d column are the following: 72 p m; 99 p m; 114 p m; 133 p m; 150 p m. Under the \u201cMelting Point\u201d column are the following: 53 K; 172 K; 266 K; 387 K; and 575 K. Under the \u201cBoiling Point\u201d column are the following: 85 K; 238 K; 332 K; 457 K; and 610 K.\">\n<thead>\n<tr valign=\"middle\">\n<th colspan=\"5\" data-align=\"center\">Melting and Boiling Points of the Halogens<\/th>\n<\/tr>\n<tr valign=\"middle\">\n<th data-align=\"center\">Halogen<\/th>\n<th data-align=\"center\">Molar Mass<\/th>\n<th data-align=\"center\">Atomic Radius<\/th>\n<th data-align=\"center\">Melting Point<\/th>\n<th data-align=\"center\">Boiling Point<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr valign=\"middle\">\n<td data-align=\"center\">fluorine, F<sub>2<\/sub><\/td>\n<td data-align=\"center\">38 g\/mol<\/td>\n<td data-align=\"center\">72 pm<\/td>\n<td data-align=\"center\">53 K<\/td>\n<td data-align=\"center\">85 K<\/td>\n<\/tr>\n<tr valign=\"middle\">\n<td data-align=\"center\">chlorine, Cl<sub>2<\/sub><\/td>\n<td data-align=\"center\">71 g\/mol<\/td>\n<td data-align=\"center\">99 pm<\/td>\n<td data-align=\"center\">172 K<\/td>\n<td data-align=\"center\">238 K<\/td>\n<\/tr>\n<tr valign=\"middle\">\n<td data-align=\"center\">bromine, Br<sub>2<\/sub><\/td>\n<td data-align=\"center\">160 g\/mol<\/td>\n<td data-align=\"center\">114 pm<\/td>\n<td data-align=\"center\">266 K<\/td>\n<td data-align=\"center\">332 K<\/td>\n<\/tr>\n<tr valign=\"middle\">\n<td data-align=\"center\">iodine, I<sub>2<\/sub><\/td>\n<td data-align=\"center\">254 g\/mol<\/td>\n<td data-align=\"center\">133 pm<\/td>\n<td data-align=\"center\">387 K<\/td>\n<td data-align=\"center\">457 K<\/td>\n<\/tr>\n<tr valign=\"middle\">\n<td data-align=\"center\">astatine, At<sub>2<\/sub><\/td>\n<td data-align=\"center\">420 g\/mol<\/td>\n<td data-align=\"center\">150 pm<\/td>\n<td data-align=\"center\">575 K<\/td>\n<td data-align=\"center\">610 K<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p id=\"fs-idm135149056\">The increase in melting and boiling points with increasing atomic\/molecular size may be rationalized by considering how the strength of dispersion forces is affected by the electronic structure of the atoms or molecules in the substance. In a larger atom, the valence electrons are, on average, farther from the nuclei than in a smaller atom. Thus, they are less tightly held and can more easily form the temporary dipoles that produce the attraction. The measure of how easy or difficult it is for another electrostatic charge (for example, a nearby ion or polar molecule) to distort a molecule\u2019s charge distribution (its electron cloud) is known as <strong>polarizability<\/strong>. A molecule that has a charge cloud that is easily distorted is said to be very polarizable and will have large dispersion forces; one with a charge cloud that is difficult to distort is not very polarizable and will have small dispersion forces.<\/p>\n<div id=\"fs-idm100317728\" class=\"textbox textbox--examples\" data-type=\"example\">\n<p id=\"fs-idp26427152\"><strong>London Forces and Their Effects<\/strong><\/p>\n<p>Order the following compounds of a group 14 element and hydrogen from lowest to highest boiling point: CH<sub>4<\/sub>, SiH<sub>4<\/sub>, GeH<sub>4<\/sub>, and SnH<sub>4<\/sub>. Explain your reasoning.<\/p>\n<p id=\"fs-idm106734480\"><span data-type=\"title\">Solution:<\/span><\/p>\n<p>Applying the skills acquired in the chapter on chemical bonding and molecular geometry, all of these compounds are predicted to be nonpolar, so they may experience only dispersion forces: the smaller the molecule, the less polarizable and the weaker the dispersion forces; the larger the molecule, the larger the dispersion forces. The molar masses of CH<sub>4<\/sub>, SiH<sub>4<\/sub>, GeH<sub>4<\/sub>, and SnH<sub>4<\/sub> are approximately 16 g\/mol, 32 g\/mol, 77 g\/mol, and 123 g\/mol, respectively. Therefore, CH<sub>4<\/sub> is expected to have the lowest boiling point and SnH<sub>4<\/sub> the highest boiling point. The ordering from lowest to highest boiling point is expected to be CH<sub>4<\/sub> &lt; SiH<sub>4<\/sub> &lt; GeH<sub>4<\/sub> &lt; SnH<sub>4<\/sub>.<\/p>\n<p id=\"fs-idp136003920\">A graph of the actual boiling points of these compounds versus the period of the group 14 element shows this prediction to be correct:<\/p>\n<p><span id=\"fs-idp63841152\" class=\"scaled-down\" data-type=\"media\" data-alt=\"A line graph, titled \u201cCarbon Family,\u201d is shown where the y-axis is labeled \u201cTemperature, ( degree sign C )\u201d and has values of \u201cnegative 200\u201d to \u201cnegative 40\u201d from bottom to top in increments of 20. The x-axis is labeled \u201cPeriod\u201d and has values of \u201c0\u201d to \u201c5\u201d in increments of 1. The first point on the graph is labeled \u201cC H subscript 4\u201d and is at point \u201c2, negative 160.\u201d The second point on the graph is labeled \u201cS i H subscript 4\u201d and is at point \u201c3, negative 120\u201d while the third point on the graph is labeled \u201cG e H subscript 4\u201d and is at point \u201c4, negative 100.\u201d The fourth point on the graph is labeled \u201cS n H subscript 4\u201d and is at point \u201c5, negative 60.\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_BoilPoints_img-1.jpg\" alt=\"A line graph, titled \u201cCarbon Family,\u201d is shown where the y-axis is labeled \u201cTemperature, ( degree sign C )\u201d and has values of \u201cnegative 200\u201d to \u201cnegative 40\u201d from bottom to top in increments of 20. The x-axis is labeled \u201cPeriod\u201d and has values of \u201c0\u201d to \u201c5\u201d in increments of 1. The first point on the graph is labeled \u201cC H subscript 4\u201d and is at point \u201c2, negative 160.\u201d The second point on the graph is labeled \u201cS i H subscript 4\u201d and is at point \u201c3, negative 120\u201d while the third point on the graph is labeled \u201cG e H subscript 4\u201d and is at point \u201c4, negative 100.\u201d The fourth point on the graph is labeled \u201cS n H subscript 4\u201d and is at point \u201c5, negative 60.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<p id=\"fs-idp128687200\"><strong>Check Your Learning:<\/strong><\/p>\n<p>Order the following hydrocarbons from lowest to highest boiling point: C<sub>2<\/sub>H<sub>6<\/sub>, C<sub>3<\/sub>H<sub>8<\/sub>, and C<sub>4<\/sub>H<sub>10<\/sub>.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"fs-idm119929280\" data-type=\"note\">\n<div data-type=\"title\"><strong>Answer:<\/strong><\/div>\n<p id=\"fs-idm93042944\">C<sub>2<\/sub>H<sub>6<\/sub> &lt; C<sub>3<\/sub>H<sub>8<\/sub> &lt; C<sub>4<\/sub>H<sub>10<\/sub>. All of these compounds are nonpolar and only have London dispersion forces: the larger the molecule, the larger the dispersion forces and the higher the boiling point. The ordering from lowest to highest boiling point is therefore C<sub>2<\/sub>H<sub>6<\/sub> &lt; C<sub>3<\/sub>H<sub>8<\/sub> &lt; C<sub>4<\/sub>H<sub>10<\/sub>.<\/p>\n<\/div>\n<\/div>\n<p id=\"fs-idm93742928\">The shapes of molecules also affect the magnitudes of the dispersion forces between them. For example, boiling points for the isomers <em data-effect=\"italics\">n<\/em>-pentane, isopentane, and neopentane (shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_PentIso\">(Figure)<\/a>) are 36 \u00b0C, 27 \u00b0C, and 9.5 \u00b0C, respectively. Even though these compounds are composed of molecules with the same chemical formula, C<sub>5<\/sub>H<sub>12<\/sub>, the difference in boiling points suggests that dispersion forces in the liquid phase are different, being greatest for <em data-effect=\"italics\">n<\/em>-pentane and least for neopentane. The elongated shape of <em data-effect=\"italics\">n<\/em>-pentane provides a greater surface area available for contact between molecules, resulting in correspondingly stronger dispersion forces. The more compact shape of isopentane offers a smaller surface area available for intermolecular contact and, therefore, weaker dispersion forces. Neopentane molecules are the most compact of the three, offering the least available surface area for intermolecular contact and, hence, the weakest dispersion forces. This behavior is analogous to the connections that may be formed between strips of VELCRO brand fasteners: the greater the area of the strip\u2019s contact, the stronger the connection.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_PentIso\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">The strength of the dispersion forces increases with the contact area between molecules, as demonstrated by the boiling points of these pentane isomers.<\/div>\n<p><span id=\"fs-idm29590512\" data-type=\"media\" data-alt=\"Three images of molecules are shown. The first shows a cluster of large, gray spheres each bonded together and to several smaller, white spheres. There is a gray, jagged line and then the mirror image of the first cluster of spheres is shown. Above these two clusters is the label, \u201cSmall contact area, weakest attraction,\u201d and below is the label, \u201cneopentane boiling point: 9.5 degrees C.\u201d The second shows a chain of three gray spheres bonded by the middle sphere to a fourth gray sphere. Each gray sphere is bonded to several smaller, white spheres. There is a jagged, gray line and then the mirror image of the first chain appears. Above these two chains is the label, \u201cLess surface area, less attraction,\u201d and below is the label, \u201cisopentane boiling point: 27 degrees C.\u201d The third image shows a chain of five gray spheres bonded together and to several smaller, white spheres. There is a jagged gray line and then the mirror image of the first chain appears. Above these chains is the label, \u201cLarge contact area, strong attraction,\u201d and below is the label, \u201cn-pentane boiling point 36 degrees C.\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_PentIso-1.jpg\" alt=\"Three images of molecules are shown. The first shows a cluster of large, gray spheres each bonded together and to several smaller, white spheres. There is a gray, jagged line and then the mirror image of the first cluster of spheres is shown. Above these two clusters is the label, \u201cSmall contact area, weakest attraction,\u201d and below is the label, \u201cneopentane boiling point: 9.5 degrees C.\u201d The second shows a chain of three gray spheres bonded by the middle sphere to a fourth gray sphere. Each gray sphere is bonded to several smaller, white spheres. There is a jagged, gray line and then the mirror image of the first chain appears. Above these two chains is the label, \u201cLess surface area, less attraction,\u201d and below is the label, \u201cisopentane boiling point: 27 degrees C.\u201d The third image shows a chain of five gray spheres bonded together and to several smaller, white spheres. There is a jagged gray line and then the mirror image of the first chain appears. Above these chains is the label, \u201cLarge contact area, strong attraction,\u201d and below is the label, \u201cn-pentane boiling point 36 degrees C.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<div id=\"fs-idp29280240\" class=\"chemistry everyday-life\" data-type=\"note\">\n<div data-type=\"title\"><\/div>\n<div data-type=\"title\"><\/div>\n<div data-type=\"title\"><strong>Geckos and Intermolecular Forces<\/strong><\/div>\n<p id=\"fs-idm15049248\">Geckos have an amazing ability to adhere to most surfaces. They can quickly run up smooth walls and across ceilings that have no toe-holds, and they do this without having suction cups or a sticky substance on their toes. And while a gecko can lift its feet easily as it walks along a surface, if you attempt to pick it up, it sticks to the surface. How are geckos (as well as spiders and some other insects) able to do this? Although this phenomenon has been investigated for hundreds of years, scientists only recently uncovered the details of the process that allows geckos\u2019 feet to behave this way.<\/p>\n<p id=\"fs-idp29466368\">Geckos\u2019 toes are covered with hundreds of thousands of tiny hairs known as <em data-effect=\"italics\">setae<\/em>, with each seta, in turn, branching into hundreds of tiny, flat, triangular tips called <em data-effect=\"italics\">spatulae<\/em>. The huge numbers of spatulae on its setae provide a gecko, shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_Geckos\">(Figure)<\/a>, with a large total surface area for sticking to a surface. In 2000, Kellar <span class=\"no-emphasis\" data-type=\"term\">Autumn<\/span>, who leads a multi-institutional gecko research team, found that geckos adhered equally well to both polar silicon dioxide and nonpolar gallium arsenide. This proved that geckos stick to surfaces because of dispersion forces\u2014weak intermolecular attractions arising from temporary, synchronized charge distributions between adjacent molecules. Although dispersion forces are very weak, the total attraction over millions of spatulae is large enough to support many times the gecko\u2019s weight.<\/p>\n<p id=\"fs-idm74321904\">In 2014, two scientists developed a model to explain how geckos can rapidly transition from \u201csticky\u201d to \u201cnon-sticky.\u201d Alex <span class=\"no-emphasis\" data-type=\"term\">Greaney<\/span> and Congcong <span class=\"no-emphasis\" data-type=\"term\">Hu<\/span> at Oregon State University described how geckos can achieve this by changing the angle between their spatulae and the surface. Geckos\u2019 feet, which are normally nonsticky, become sticky when a small shear force is applied. By curling and uncurling their toes, geckos can alternate between sticking and unsticking from a surface, and thus easily move across it. Further investigations may eventually lead to the development of better adhesives and other applications.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_Geckos\" class=\"bc-figure figure\">\n<div class=\"bc-figcaption figcaption\">Geckos\u2019 toes contain large numbers of tiny hairs (setae), which branch into many triangular tips (spatulae). Geckos adhere to surfaces because of van der Waals attractions between the surface and a gecko\u2019s millions of spatulae. By changing how the spatulae contact the surface, geckos can turn their stickiness \u201con\u201d and \u201coff.\u201d (credit photo: modification of work by \u201cJC*+A!\u201d\/Flickr)<\/div>\n<p><span id=\"fs-idp79180464\" data-type=\"media\" data-alt=\"Three figures are shown. The first is a photo of the bottom of a gecko\u2019s foot. The second is bigger version which shows the setae. The third is a bigger version of the setae and shows the spatulae.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_Geckos-1.jpg\" alt=\"Three figures are shown. The first is a photo of the bottom of a gecko\u2019s foot. The second is bigger version which shows the setae. The third is a bigger version of the setae and shows the spatulae.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idp133005728\" class=\"chemistry link-to-learning\" data-type=\"note\">\n<p id=\"fs-idm71587872\">Watch this <a href=\"http:\/\/openstaxcollege.org\/l\/16kellaraut\">video<\/a> to learn more about Kellar Autumn\u2019s research that determined that van der Waals forces are responsible for a gecko\u2019s ability to cling and climb.<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idp3278832\" class=\"bc-section section\" data-depth=\"1\">\n<h3 data-type=\"title\"><strong>Dipole-Dipole Attractions<\/strong><\/h3>\n<p id=\"fs-idm25328160\">Recall from the chapter on chemical bonding and molecular geometry that <em data-effect=\"italics\">polar<\/em> molecules have a partial positive charge on one side and a partial negative charge on the other side of the molecule\u2014a separation of charge called a <em data-effect=\"italics\">dipole<\/em>. Consider a polar molecule such as hydrogen chloride, HCl. In the HCl molecule, the more electronegative Cl atom bears the partial negative charge, whereas the less electronegative H atom bears the partial positive charge. An attractive force between HCl molecules results from the attraction between the positive end of one HCl molecule and the negative end of another. This attractive force is called a <strong>dipole-dipole attraction<\/strong>\u2014the electrostatic force between the partially positive end of one polar molecule and the partially negative end of another, as illustrated in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_DipDip\">(Figure)<\/a>.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_DipDip\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">This image shows two arrangements of polar molecules, such as HCl, that allow an attraction between the partial negative end of one molecule and the partial positive end of another.<\/div>\n<p><span id=\"fs-idp12575856\" data-type=\"media\" data-alt=\"Two pairs of molecules are shown where each molecule has one larger blue side labeled \u201cdelta sign, negative sign\u201d and a smaller red side labeled \u201cdelta sign, positive sign. In the first pair, the red sides of the two molecules both face to the left and the blue side to the right. A horizontal dotted line lies in between the two. In the second pair, the molecules face up and down, with the red and blue ends aligning. A horizontal dotted line lies between the red and blue ends facing upward and another lies between the red and blue ends facing downward.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_DipDip-1.jpg\" alt=\"Two pairs of molecules are shown where each molecule has one larger blue side labeled \u201cdelta sign, negative sign\u201d and a smaller red side labeled \u201cdelta sign, positive sign. In the first pair, the red sides of the two molecules both face to the left and the blue side to the right. A horizontal dotted line lies in between the two. In the second pair, the molecules face up and down, with the red and blue ends aligning. A horizontal dotted line lies between the red and blue ends facing upward and another lies between the red and blue ends facing downward.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idp108426992\">The effect of a dipole-dipole attraction is apparent when we compare the properties of HCl molecules to nonpolar F<sub>2<\/sub> molecules. Both HCl and F<sub>2<\/sub> consist of the same number of atoms and have approximately the same molecular mass. At a temperature of 150 K, molecules of both substances would have the same average KE. However, the dipole-dipole attractions between HCl molecules are sufficient to cause them to \u201cstick together\u201d to form a liquid, whereas the relatively weaker dispersion forces between nonpolar F<sub>2<\/sub> molecules are not, and so this substance is gaseous at this temperature. The higher normal boiling point of HCl (188 K) compared to F<sub>2<\/sub> (85 K) is a reflection of the greater strength of dipole-dipole attractions between HCl molecules, compared to the attractions between nonpolar F<sub>2<\/sub> molecules. We will often use values such as boiling or freezing points, or enthalpies of vaporization or fusion, as indicators of the relative strengths of IMFs of attraction present within different substances.<\/p>\n<div id=\"fs-idm116129040\" class=\"textbox textbox--examples\" data-type=\"example\">\n<p id=\"fs-idm21276784\"><strong>Dipole-Dipole Forces and Their Effects:<\/strong><\/p>\n<p>Predict which will have the higher boiling point: N<sub>2<\/sub> or CO. Explain your reasoning.<\/p>\n<p id=\"fs-idm69572480\"><strong>Solution:<\/strong><\/p>\n<p>CO and N<sub>2<\/sub> are both diatomic molecules with masses of about 28 u, so they experience similar London dispersion forces. Because CO is a polar molecule, it experiences dipole-dipole attractions. Because N<sub>2<\/sub> is nonpolar, its molecules cannot exhibit dipole-dipole attractions. The dipole-dipole attractions between CO molecules are comparably stronger than the dispersion forces between nonpolar N<sub>2<\/sub> molecules, so CO is expected to have the higher boiling point.<\/p>\n<p>&nbsp;<\/p>\n<p id=\"fs-idp56618608\"><strong>Check Your Learning:<\/strong><\/p>\n<p>Predict which will have the higher boiling point: ICl or Br<sub>2<\/sub>. Explain your reasoning.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"fs-idm21037552\" data-type=\"note\">\n<div data-type=\"title\"><strong>Answer:<\/strong><\/div>\n<p id=\"fs-idp57843568\">ICl. ICl and Br<sub>2<\/sub> have similar masses (~160 u) and therefore experience similar London dispersion forces. ICl is polar and thus also exhibits dipole-dipole attractions; Br<sub>2<\/sub> is nonpolar and does not. The relatively stronger dipole-dipole attractions require more energy to overcome, so ICl will have the higher boiling point.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idp42198272\" class=\"bc-section section\" data-depth=\"1\">\n<h3 data-type=\"title\"><strong>Hydrogen Bonding<\/strong><\/h3>\n<p id=\"fs-idp18167328\">Nitrosyl fluoride (ONF, molecular mass 49 u) is a gas at room temperature. Water (H<sub>2<\/sub>O, molecular mass 18 u) is a liquid, even though it has a lower molecular mass. We clearly cannot attribute this difference between the two compounds to dispersion forces. Both molecules have about the same shape and ONF is the heavier and larger molecule. It is, therefore, expected to experience more significant dispersion forces. Additionally, we cannot attribute this difference in boiling points to differences in the dipole moments of the molecules. Both molecules are polar and exhibit comparable dipole moments. The large difference between the boiling points is due to a particularly strong dipole-dipole attraction that may occur when a molecule contains a hydrogen atom bonded to a fluorine, oxygen, or nitrogen atom (the three most electronegative elements). The very large difference in electronegativity between the H atom (2.1) and the atom to which it is bonded (4.0 for an F atom, 3.5 for an O atom, or 3.0 for a N atom), combined with the very small size of a H atom and the relatively small sizes of F, O, or N atoms, leads to <em data-effect=\"italics\">highly concentrated partial charges<\/em> with these atoms. Molecules with F-H, O-H, or N-H moieties are very strongly attracted to similar moieties in nearby molecules, a particularly strong type of dipole-dipole attraction called <strong>hydrogen bonding<\/strong>. Examples of hydrogen bonds include HF\u22efHF, H<sub>2<\/sub>O\u22efHOH, and H<sub>3<\/sub>N\u22efHNH<sub>2<\/sub>, in which the hydrogen bonds are denoted by dots. <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_HBonding\">(Figure)<\/a> illustrates hydrogen bonding between water molecules.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_HBonding\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">Water molecules participate in multiple hydrogen-bonding interactions with nearby water molecules.<\/div>\n<p><span id=\"fs-idp29073168\" data-type=\"media\" data-alt=\"Five water molecules are shown near one another, but not touching. A dotted line lies between many of the hydrogen atoms on one molecule and the oxygen atom on another molecule.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_HBonding-1.jpg\" alt=\"Five water molecules are shown near one another, but not touching. A dotted line lies between many of the hydrogen atoms on one molecule and the oxygen atom on another molecule.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idp128658848\">Despite use of the word \u201cbond,\u201d keep in mind that hydrogen bonds are <em data-effect=\"italics\">intermolecular<\/em> attractive forces, not <em data-effect=\"italics\">intramolecular<\/em> attractive forces (covalent bonds). Hydrogen bonds are much weaker than covalent bonds, only about 5 to 10% as strong, but are generally much stronger than other dipole-dipole attractions and dispersion forces.<\/p>\n<p id=\"fs-idp20088928\">Hydrogen bonds have a pronounced effect on the properties of condensed phases (liquids and solids). For example, consider the trends in boiling points for the binary hydrides of group 15 (NH<sub>3<\/sub>, PH<sub>3<\/sub>, AsH<sub>3<\/sub>, and SbH<sub>3<\/sub>), group 16 hydrides (H<sub>2<\/sub>O, H<sub>2<\/sub>S, H<sub>2<\/sub>Se, and H<sub>2<\/sub>Te), and group 17 hydrides (HF, HCl, HBr, and HI). The boiling points of the heaviest three hydrides for each group are plotted in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_HydrideBP1\">(Figure)<\/a>. As we progress down any of these groups, the polarities of the molecules decrease slightly, whereas the sizes of the molecules increase substantially. The effect of increasingly stronger dispersion forces dominates that of increasingly weaker dipole-dipole attractions, and the boiling points are observed to increase steadily.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_HydrideBP1\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">For the group 15, 16, and 17 hydrides, the boiling points for each class of compounds increase with increasing molecular mass for elements in periods 3, 4, and 5.<\/div>\n<p><span id=\"fs-idm21286928\" data-type=\"media\" data-alt=\"A line graph is shown where the y-axis is labeled \u201cBoiling point (, degree sign, C )\u201d and has values of \u201c negative 150\u201d to \u201c150\u201d from bottom to top in increments of 50. The x-axis is labeled \u201cPeriod\u201d and has values of \u201c0\u201d to \u201c5\u201d in increments of 1. Three lines are shown on the graph and are labeled in the legend. The red line is labeled as \u201chalogen family,\u201d the blue is \u201coxygen family\u201d and the green is \u201cnitrogen family.\u201d The first point on the red line is labeled \u201cquestion mark\u201d and is at point \u201c2, negative 120\u201d. The second point on the line is labeled \u201cH C l\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cH B r\u201d and is at point \u201c4, negative 60\u201d. The fourth point on the line is labeled \u201cH I\u201d and is at point \u201c5, negative 40.\u201d The first point on the green line is labeled \u201cquestion mark\u201d and is at point \u201c2, negative 125.\u201d The second point on the line is labeled \u201cP H, subscript 3\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cA s H, subscript 3\u201d and is at point \u201c4, negative 55.\u201d The fourth point on the line is labeled \u201cS b H, subscript 3\u201d and is at point \u201c5, negative 10.\u201d The first point on the blue line is labeled \u201cquestion mark\u201d and is at point \u201c2, negative 80.\u201d The second point on the line is labeled \u201cH, subscript 2, S\u201d and is at point \u201c3, negative 55\u201d while the third point on the line is labeled \u201cH, subscript 2, S e\u201d and is at point \u201c4, negative 45.\u201d The fourth point on the line is labeled \u201cH, subscript 2, T e\u201d and is at point \u201c5, negative 3.\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_HydrideBP1-1.jpg\" alt=\"A line graph is shown where the y-axis is labeled \u201cBoiling point (, degree sign, C )\u201d and has values of \u201c negative 150\u201d to \u201c150\u201d from bottom to top in increments of 50. The x-axis is labeled \u201cPeriod\u201d and has values of \u201c0\u201d to \u201c5\u201d in increments of 1. Three lines are shown on the graph and are labeled in the legend. The red line is labeled as \u201chalogen family,\u201d the blue is \u201coxygen family\u201d and the green is \u201cnitrogen family.\u201d The first point on the red line is labeled \u201cquestion mark\u201d and is at point \u201c2, negative 120\u201d. The second point on the line is labeled \u201cH C l\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cH B r\u201d and is at point \u201c4, negative 60\u201d. The fourth point on the line is labeled \u201cH I\u201d and is at point \u201c5, negative 40.\u201d The first point on the green line is labeled \u201cquestion mark\u201d and is at point \u201c2, negative 125.\u201d The second point on the line is labeled \u201cP H, subscript 3\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cA s H, subscript 3\u201d and is at point \u201c4, negative 55.\u201d The fourth point on the line is labeled \u201cS b H, subscript 3\u201d and is at point \u201c5, negative 10.\u201d The first point on the blue line is labeled \u201cquestion mark\u201d and is at point \u201c2, negative 80.\u201d The second point on the line is labeled \u201cH, subscript 2, S\u201d and is at point \u201c3, negative 55\u201d while the third point on the line is labeled \u201cH, subscript 2, S e\u201d and is at point \u201c4, negative 45.\u201d The fourth point on the line is labeled \u201cH, subscript 2, T e\u201d and is at point \u201c5, negative 3.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idp26510624\">If we use this trend to predict the boiling points for the lightest hydride for each group, we would expect NH<sub>3<\/sub> to boil at about \u2212120 \u00b0C, H<sub>2<\/sub>O to boil at about \u221280 \u00b0C, and HF to boil at about \u2212110 \u00b0C. However, when we measure the boiling points for these compounds, we find that they are dramatically higher than the trends would predict, as shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_HydrideBP2\">(Figure)<\/a>. The stark contrast between our na\u00efve predictions and reality provides compelling evidence for the strength of hydrogen bonding.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_HydrideBP2\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">In comparison to periods 3\u22125, the binary hydrides of period 2 elements in groups 17, 16 and 15 (F, O and N, respectively) exhibit anomalously high boiling points due to hydrogen bonding.<\/div>\n<p><span id=\"fs-idp79204320\" data-type=\"media\" data-alt=\"A line graph is shown where the y-axis is labeled \u201cBoiling point, ( degree sign, C )\u201d and has values of \u201cnegative 150\u201d to \u201c150\u201d from bottom to top in increments of 50. The x-axis is labeled \u201cPeriod\u201d and has values of \u201c0\u201d to \u201c5\u201d in increments of 1. Three lines are shown on the graph and are labeled in the legend. The red line is labeled as \u201chalogen family,\u201d the blue is \u201coxygen family\u201d and the green is \u201cnitrogen family.\u201d The first point on the red line is labeled \u201cH F\u201d and is at point \u201c2, 25.\u201d The second point on the line is labeled \u201cH C l\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cH B r\u201d and is at point \u201c4, negative 60.\u201d The fourth point on the line is labeled \u201cH I\u201d and is at point \u201c5, negative 40.\u201d The first point on the green line is labeled \u201cN H, subscript 3\u201d and is at point \u201c2, negative 40.\u201d The second point on the line is labeled \u201cP H, subscript 3\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cA s H, subscript 3\u201d and is at point \u201c4, negative 55.\u201d The fourth point on the line is labeled \u201cS b H, subscript 3\u201d and is at point \u201c5, negative 10.\u201d The first point on the blue line is labeled \u201cH, subscript 2, O\u201d and is at point \u201c2, 100.\u201d The second point on the line is labeled \u201cH, subscript 2, S\u201d and is at point \u201c3, negative 55\u201d while the third point on the line is labeled \u201cH, subscript 2, S e\u201d and is at point \u201c4, negative 45.\u201d The fourth point on the line is labeled \u201cH, subscript 2, T e\u201d and is at point \u201c5, negative 3.\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_HydrideBP2-1.jpg\" alt=\"A line graph is shown where the y-axis is labeled \u201cBoiling point, ( degree sign, C )\u201d and has values of \u201cnegative 150\u201d to \u201c150\u201d from bottom to top in increments of 50. The x-axis is labeled \u201cPeriod\u201d and has values of \u201c0\u201d to \u201c5\u201d in increments of 1. Three lines are shown on the graph and are labeled in the legend. The red line is labeled as \u201chalogen family,\u201d the blue is \u201coxygen family\u201d and the green is \u201cnitrogen family.\u201d The first point on the red line is labeled \u201cH F\u201d and is at point \u201c2, 25.\u201d The second point on the line is labeled \u201cH C l\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cH B r\u201d and is at point \u201c4, negative 60.\u201d The fourth point on the line is labeled \u201cH I\u201d and is at point \u201c5, negative 40.\u201d The first point on the green line is labeled \u201cN H, subscript 3\u201d and is at point \u201c2, negative 40.\u201d The second point on the line is labeled \u201cP H, subscript 3\u201d and is at point \u201c3, negative 80\u201d while the third point on the line is labeled \u201cA s H, subscript 3\u201d and is at point \u201c4, negative 55.\u201d The fourth point on the line is labeled \u201cS b H, subscript 3\u201d and is at point \u201c5, negative 10.\u201d The first point on the blue line is labeled \u201cH, subscript 2, O\u201d and is at point \u201c2, 100.\u201d The second point on the line is labeled \u201cH, subscript 2, S\u201d and is at point \u201c3, negative 55\u201d while the third point on the line is labeled \u201cH, subscript 2, S e\u201d and is at point \u201c4, negative 45.\u201d The fourth point on the line is labeled \u201cH, subscript 2, T e\u201d and is at point \u201c5, negative 3.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<div id=\"fs-idm118983568\" class=\"textbox textbox--examples\" data-type=\"example\">\n<p id=\"fs-idp138845584\"><strong>Effect of Hydrogen Bonding on Boiling Points:<\/strong><\/p>\n<p>Consider the compounds dimethylether (CH<sub>3<\/sub>OCH<sub>3<\/sub>), ethanol (CH<sub>3<\/sub>CH<sub>2<\/sub>OH), and propane (CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>3<\/sub>). Their boiling points, not necessarily in order, are \u221242.1 \u00b0C, \u221224.8 \u00b0C, and 78.4 \u00b0C. Match each compound with its boiling point. Explain your reasoning.<\/p>\n<p>&nbsp;<\/p>\n<p id=\"fs-idm50766656\"><strong>Solution:<\/strong><\/p>\n<p>The VSEPR-predicted shapes of CH<sub>3<\/sub>OCH<sub>3<\/sub>, CH<sub>3<\/sub>CH<sub>2<\/sub>OH, and CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>3<\/sub> are similar, as are their molar masses (46 g\/mol, 46 g\/mol, and 44 g\/mol, respectively), so they will exhibit similar dispersion forces. Since CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>3<\/sub> is nonpolar, it may exhibit <em data-effect=\"italics\">only<\/em> dispersion forces. Because CH<sub>3<\/sub>OCH<sub>3<\/sub> is polar, it will also experience dipole-dipole attractions. Finally, CH<sub>3<\/sub>CH<sub>2<\/sub>OH has an \u2212OH group, and so it will experience the uniquely strong dipole-dipole attraction known as hydrogen bonding. So the ordering in terms of strength of IMFs, and thus boiling points, is CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>3<\/sub> &lt; CH<sub>3<\/sub>OCH<sub>3<\/sub> &lt; CH<sub>3<\/sub>CH<sub>2<\/sub>OH. The boiling point of propane is \u221242.1 \u00b0C, the boiling point of dimethylether is \u221224.8 \u00b0C, and the boiling point of ethanol is 78.5 \u00b0C.<\/p>\n<p>&nbsp;<\/p>\n<p id=\"fs-idm47706096\"><strong>Check Your Learning:<\/strong><\/p>\n<p>Ethane (CH<sub>3<\/sub>CH<sub>3<\/sub>) has a melting point of \u2212183 \u00b0C and a boiling point of \u221289 \u00b0C. Predict the melting and boiling points for methylamine (CH<sub>3<\/sub>NH<sub>2<\/sub>). Explain your reasoning.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"fs-idm67186592\" data-type=\"note\">\n<div data-type=\"title\"><strong>Answer:<\/strong><\/div>\n<p id=\"fs-idm91556848\">The melting point and boiling point for methylamine are predicted to be significantly greater than those of ethane. CH<sub>3<\/sub>CH<sub>3<\/sub> and CH<sub>3<\/sub>NH<sub>2<\/sub> are similar in size and mass, but methylamine possesses an \u2212NH group and therefore may exhibit hydrogen bonding. This greatly increases its IMFs, and therefore its melting and boiling points. It is difficult to predict values, but the known values are a melting point of \u221293 \u00b0C and a boiling point of \u22126 \u00b0C.<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm44601856\" class=\"chemistry sciences-interconnect\" data-type=\"note\">\n<div data-type=\"title\"><\/div>\n<div data-type=\"title\"><strong>Hydrogen Bonding and DNA<\/strong><\/div>\n<p id=\"fs-idm79852624\">Deoxyribonucleic acid (DNA) is found in every living organism and contains the genetic information that determines the organism\u2019s characteristics, provides the blueprint for making the proteins necessary for life, and serves as a template to pass this information on to the organism\u2019s offspring. A DNA molecule consists of two (anti-)parallel chains of repeating nucleotides, which form its well-known double helical structure, as shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_DNA\">(Figure)<\/a>.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_DNA\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">Two separate DNA molecules form a double-stranded helix in which the molecules are held together via hydrogen bonding. (credit: modification of work by Jerome Walker, Dennis Myts)<\/div>\n<p><span id=\"fs-idm97606608\" data-type=\"media\" data-alt=\"Two images are shown. The first lies on the left side of the page and shows a helical structure like a twisted ladder where the rungs of the ladder, labeled \u201cBase pair\u201d are red, yellow, green and blue paired bars. The red and yellow bars, which are always paired together, are labeled in the legend, which is titled \u201cNitrogenous bases\u201d as \u201cadenine\u201d and \u201cthymine,\u201d respectively. The blue and green bars, which are always paired together, are labeled in the legend as \u201cguanine\u201d and \u201ccytosine,\u201d respectively. At the top of the helical structure, the left-hand side rail, or \u201cSugar, dash, phosphate backbone,\u201d is labeled as \u201c3, prime\u201d while the right is labeled as \u201c5, prime.\u201d These labels are reversed at the bottom of the helix. To the right of the page is a large Lewis structure. The top left corner of this structure, labeled \u201c5, prime,\u201d shows a phosphorus atom single bonded to three oxygen atoms, one of which has a superscripted negative charge, and double bonded to a fourth oxygen atom. One of the single bonded oxygen atoms is single bonded to the left corner of a five-membered ring with an oxygen atom at its top point and which is single bonded to an oxygen atom on the bottom left. This oxygen atom is single bonded to a phosphorus atom that is single bonded to two other hydrogen atoms and double bonded to a fourth oxygen atom. The lower left of these oxygen atoms is single bonded to another oxygen atom that is single bonded to a five-membered ring with an oxygen in the upper bonding site. The bottom left of this ring has a hydroxyl group attached to it while the upper right carbon is single bonded to a nitrogen atom that is part of a five-membered ring bonded to a six-membered ring. Both of these rings have points of unsaturation and nitrogen atoms bonded into their structures. On the right side of the six-membered ring are two single bonded amine groups and a double bonded oxygen. Three separate dotted lines extend from these sites to corresponding sites on a second six-membered ring. This ring has points of unsaturation and a nitrogen atom in the bottom right bonding position that is single bonded to a five-membered ring on the right side of the image. This ring is single bonded to a carbon that is single bonded to an oxygen that is single bonded to a phosphorus. The phosphorus is single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. This group is labeled \u201c5, prime.\u201d The five-membered ring is also bonded on the top side to an oxygen that is bonded to a phosphorus single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. The upper left oxygen of this group is single bonded to a carbon that is single bonded to a five-membered ring with an oxygen in the bottom bonding position. This ring has a hydroxyl group on its upper right side that is labeled \u201c3, prime\u201d and is bonded on the left side to a nitrogen that is a member of a five-membered ring. This ring is bonded to a six-membered ring and both have points of unsaturation. This ring has a nitrogen on the left side, as well as an amine group, that have two dotted lines leading from them to an oxygen and amine group on a six membered ring. These dotted lines are labeled \u201cHydrogen bonds.\u201d The six membered ring also has a double bonded oxygen on its lower side and a nitrogen atom on its left side that is single bonded to a five-membered ring. This ring connects to the two phosphate groups mentioned at the start of this to form a large circle. The name \u201cguanine\u201d is written below the lower left side of this image while the name \u201ccytosine\u201d is written on the lower right. The name \u201cthymine\u201d is written above the right side of the image and \u201cadenine\u201d is written on the top right. Three sections are indicated below the images where the left is labeled \u201cSugar, dash, phosphate backbone,\u201d the middle is labeled \u201cBases\u201d and the right is labeled \u201cSugar, dash, phosphate backbone.\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_DNA-1.jpg\" alt=\"Two images are shown. The first lies on the left side of the page and shows a helical structure like a twisted ladder where the rungs of the ladder, labeled \u201cBase pair\u201d are red, yellow, green and blue paired bars. The red and yellow bars, which are always paired together, are labeled in the legend, which is titled \u201cNitrogenous bases\u201d as \u201cadenine\u201d and \u201cthymine,\u201d respectively. The blue and green bars, which are always paired together, are labeled in the legend as \u201cguanine\u201d and \u201ccytosine,\u201d respectively. At the top of the helical structure, the left-hand side rail, or \u201cSugar, dash, phosphate backbone,\u201d is labeled as \u201c3, prime\u201d while the right is labeled as \u201c5, prime.\u201d These labels are reversed at the bottom of the helix. To the right of the page is a large Lewis structure. The top left corner of this structure, labeled \u201c5, prime,\u201d shows a phosphorus atom single bonded to three oxygen atoms, one of which has a superscripted negative charge, and double bonded to a fourth oxygen atom. One of the single bonded oxygen atoms is single bonded to the left corner of a five-membered ring with an oxygen atom at its top point and which is single bonded to an oxygen atom on the bottom left. This oxygen atom is single bonded to a phosphorus atom that is single bonded to two other hydrogen atoms and double bonded to a fourth oxygen atom. The lower left of these oxygen atoms is single bonded to another oxygen atom that is single bonded to a five-membered ring with an oxygen in the upper bonding site. The bottom left of this ring has a hydroxyl group attached to it while the upper right carbon is single bonded to a nitrogen atom that is part of a five-membered ring bonded to a six-membered ring. Both of these rings have points of unsaturation and nitrogen atoms bonded into their structures. On the right side of the six-membered ring are two single bonded amine groups and a double bonded oxygen. Three separate dotted lines extend from these sites to corresponding sites on a second six-membered ring. This ring has points of unsaturation and a nitrogen atom in the bottom right bonding position that is single bonded to a five-membered ring on the right side of the image. This ring is single bonded to a carbon that is single bonded to an oxygen that is single bonded to a phosphorus. The phosphorus is single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. This group is labeled \u201c5, prime.\u201d The five-membered ring is also bonded on the top side to an oxygen that is bonded to a phosphorus single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. The upper left oxygen of this group is single bonded to a carbon that is single bonded to a five-membered ring with an oxygen in the bottom bonding position. This ring has a hydroxyl group on its upper right side that is labeled \u201c3, prime\u201d and is bonded on the left side to a nitrogen that is a member of a five-membered ring. This ring is bonded to a six-membered ring and both have points of unsaturation. This ring has a nitrogen on the left side, as well as an amine group, that have two dotted lines leading from them to an oxygen and amine group on a six membered ring. These dotted lines are labeled \u201cHydrogen bonds.\u201d The six membered ring also has a double bonded oxygen on its lower side and a nitrogen atom on its left side that is single bonded to a five-membered ring. This ring connects to the two phosphate groups mentioned at the start of this to form a large circle. The name \u201cguanine\u201d is written below the lower left side of this image while the name \u201ccytosine\u201d is written on the lower right. The name \u201cthymine\u201d is written above the right side of the image and \u201cadenine\u201d is written on the top right. Three sections are indicated below the images where the left is labeled \u201cSugar, dash, phosphate backbone,\u201d the middle is labeled \u201cBases\u201d and the right is labeled \u201cSugar, dash, phosphate backbone.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idp113560512\">Each nucleotide contains a (deoxyribose) sugar bound to a phosphate group on one side, and one of four nitrogenous bases on the other. Two of the bases, cytosine (C) and thymine (T), are single-ringed structures known as pyrimidines. The other two, adenine (A) and guanine (G), are double-ringed structures called purines. These bases form complementary base pairs consisting of one purine and one pyrimidine, with adenine pairing with thymine, and cytosine with guanine. Each base pair is held together by hydrogen bonding. A and T share two hydrogen bonds, C and G share three, and both pairings have a similar shape and structure <a class=\"autogenerated-content\" href=\"#CNX_Chem_10_01_DNA2\">(Figure)<\/a>.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_10_01_DNA2\" class=\"bc-figure figure\">\n<div class=\"bc-figcaption figcaption\">The geometries of the base molecules result in maximum hydrogen bonding between adenine and thymine (AT) and between guanine and cytosine (GC), so-called \u201ccomplementary base pairs.\u201d<\/div>\n<p><span id=\"fs-idm64449536\" data-type=\"media\" data-alt=\"A large Lewis structure is shown. The top left corner of this structure, labeled \u201c5, prime,\u201d shows a phosphorus atom single bonded to three oxygen atoms, one of which has a superscripted negative charge, and double bonded to a fourth oxygen atom. One of the single bonded oxygen atoms is single bonded to the left corner of a five-membered ring with an oxygen atom at its top point and which is single bonded to an oxygen atom on the bottom left. This oxygen atom is single bonded to a phosphorus atom that is single bonded to two other hydrogen atoms and double bonded to a fourth oxygen atom. The lower left of these oxygen atoms is single bonded to another oxygen atom that is single bonded to a five-membered ring with an oxygen in the upper bonding site. The bottom left of this ring has a hydroxyl group attached to it while the upper right carbon is single bonded to a nitrogen atom that is part of a five-membered ring bonded to a six-membered ring. Both of these rings have points of unsaturation and nitrogen atoms bonded into their structures. On the right side of the six-membered ring are two single bonded amine groups and a double bonded oxygen. Three separate dotted lines extend from these sites to corresponding sites on a second six-membered ring. This ring has points of unsaturation and a nitrogen atom in the bottom right bonding position that is single bonded to a five-membered ring on the right side of the image. This ring is single bonded to a carbon that is single bonded to an oxygen that is single bonded to a phosphorus. The phosphorus is single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. This group is labeled \u201c5, prime.\u201d The five-membered ring is also bonded on the top side to an oxygen that is bonded to a phosphorus single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. The upper left oxygen of this group is single bonded to a carbon that is single bonded to a five-membered ring with an oxygen in the bottom bonding position. This ring has a hydroxyl group on its upper right side that is labeled \u201c3, prime\u201d and is bonded on the left side to a nitrogen that is a member of a five-membered ring. This ring is bonded to a six-membered ring and both have points of unsaturation. This ring has a nitrogen on the left side, as well as an amine group, that have two dotted lines leading from them to an oxygen and amine group on a six membered ring. These dotted lines are labeled \u201cHydrogen bonds.\u201d The six membered ring also has a double bonded oxygen on its lower side and a nitrogen atom on its left side that is single bonded to a five-membered ring. This ring connects to the two phosphate groups mentioned at the start of this to form a large circle. The name \u201cguanine\u201d is written below the lower left side of this image while the name \u201ccytosine\u201d is written on the lower right. The name \u201cthymine\u201d is written above the right side of the image and \u201cadenine\u201d is written on the top right. Three sections are indicated below the images where the left is labeled \u201cSugar, dash, phosphate backbone,\u201d the middle is labeled \u201cBases\u201d and the right is labeled \u201cSugar, dash, phosphate backbone.\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_10_01_DNA2-1.jpg\" alt=\"A large Lewis structure is shown. The top left corner of this structure, labeled \u201c5, prime,\u201d shows a phosphorus atom single bonded to three oxygen atoms, one of which has a superscripted negative charge, and double bonded to a fourth oxygen atom. One of the single bonded oxygen atoms is single bonded to the left corner of a five-membered ring with an oxygen atom at its top point and which is single bonded to an oxygen atom on the bottom left. This oxygen atom is single bonded to a phosphorus atom that is single bonded to two other hydrogen atoms and double bonded to a fourth oxygen atom. The lower left of these oxygen atoms is single bonded to another oxygen atom that is single bonded to a five-membered ring with an oxygen in the upper bonding site. The bottom left of this ring has a hydroxyl group attached to it while the upper right carbon is single bonded to a nitrogen atom that is part of a five-membered ring bonded to a six-membered ring. Both of these rings have points of unsaturation and nitrogen atoms bonded into their structures. On the right side of the six-membered ring are two single bonded amine groups and a double bonded oxygen. Three separate dotted lines extend from these sites to corresponding sites on a second six-membered ring. This ring has points of unsaturation and a nitrogen atom in the bottom right bonding position that is single bonded to a five-membered ring on the right side of the image. This ring is single bonded to a carbon that is single bonded to an oxygen that is single bonded to a phosphorus. The phosphorus is single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. This group is labeled \u201c5, prime.\u201d The five-membered ring is also bonded on the top side to an oxygen that is bonded to a phosphorus single bonded to two other oxygen atoms and double bonded to a fourth oxygen atom. The upper left oxygen of this group is single bonded to a carbon that is single bonded to a five-membered ring with an oxygen in the bottom bonding position. This ring has a hydroxyl group on its upper right side that is labeled \u201c3, prime\u201d and is bonded on the left side to a nitrogen that is a member of a five-membered ring. This ring is bonded to a six-membered ring and both have points of unsaturation. This ring has a nitrogen on the left side, as well as an amine group, that have two dotted lines leading from them to an oxygen and amine group on a six membered ring. These dotted lines are labeled \u201cHydrogen bonds.\u201d The six membered ring also has a double bonded oxygen on its lower side and a nitrogen atom on its left side that is single bonded to a five-membered ring. This ring connects to the two phosphate groups mentioned at the start of this to form a large circle. The name \u201cguanine\u201d is written below the lower left side of this image while the name \u201ccytosine\u201d is written on the lower right. The name \u201cthymine\u201d is written above the right side of the image and \u201cadenine\u201d is written on the top right. Three sections are indicated below the images where the left is labeled \u201cSugar, dash, phosphate backbone,\u201d the middle is labeled \u201cBases\u201d and the right is labeled \u201cSugar, dash, phosphate backbone.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idp108968272\">The cumulative effect of millions of hydrogen bonds effectively holds the two strands of DNA together. Importantly, the two strands of DNA can relatively easily \u201cunzip\u201d down the middle since hydrogen bonds are relatively weak compared to the covalent bonds that hold the atoms of the individual DNA molecules together. This allows both strands to function as a template for replication.<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm78986320\" class=\"summary\" data-depth=\"1\">\n<h3 data-type=\"title\"><strong>Key Concepts and Summary<\/strong><\/h3>\n<p id=\"fs-idp42400528\">The physical properties of condensed matter (liquids and solids) can be explained in terms of the kinetic molecular theory. In a liquid, intermolecular attractive forces hold the molecules in contact, although they still have sufficient KE to move past each other.<\/p>\n<p id=\"fs-idp113514832\">Intermolecular attractive forces, collectively referred to as van der Waals forces, are responsible for the behavior of liquids and solids and are electrostatic in nature. Dipole-dipole attractions result from the electrostatic attraction of the partial negative end of one dipolar molecule for the partial positive end of another. The temporary dipole that results from the motion of the electrons in an atom can induce a dipole in an adjacent atom and give rise to the London dispersion force. London forces increase with increasing molecular size. Hydrogen bonds are a special type of dipole-dipole attraction that results when hydrogen is bonded to one of the three most electronegative elements: F, O, or N.<\/p>\n<\/div>\n<div id=\"fs-idp29893056\" class=\"exercises\" data-depth=\"1\">\n<div id=\"fs-idp70845808\" data-type=\"exercise\">\n<div id=\"fs-idm12315280\" data-type=\"problem\"><\/div>\n<\/div>\n<div id=\"fs-idp18248944\" data-type=\"exercise\">\n<div id=\"fs-idp1597760\" data-type=\"solution\">\n<p id=\"fs-idm63875504\">\n<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox shaded\" data-type=\"glossary\">\n<h3 data-type=\"glossary-title\"><strong>Glossary<\/strong><\/h3>\n<dl id=\"fs-idp127496336\">\n<dt>dipole-dipole attraction<\/dt>\n<dd id=\"fs-idm18049984\">intermolecular attraction between two permanent dipoles<\/dd>\n<\/dl>\n<dl id=\"fs-idm16566240\">\n<dt>dispersion force<\/dt>\n<dd id=\"fs-idm58382832\">(also, London dispersion force) attraction between two rapidly fluctuating, temporary dipoles; significant only when particles are very close together<\/dd>\n<\/dl>\n<dl id=\"fs-idp18243872\">\n<dt>hydrogen bonding<\/dt>\n<dd id=\"fs-idm24342960\">occurs when exceptionally strong dipoles attract; bonding that exists when hydrogen is bonded to one of the three most electronegative elements: F, O, or N<\/dd>\n<\/dl>\n<dl id=\"fs-idm31438528\">\n<dt>induced dipole<\/dt>\n<dd id=\"fs-idm98054496\">temporary dipole formed when the electrons of an atom or molecule are distorted by the instantaneous dipole of a neighboring atom or molecule<\/dd>\n<\/dl>\n<dl id=\"fs-idp127211536\">\n<dt>instantaneous dipole<\/dt>\n<dd id=\"fs-idm23826208\">temporary dipole that occurs for a brief moment in time when the electrons of an atom or molecule are distributed asymmetrically<\/dd>\n<\/dl>\n<dl id=\"fs-idm66585952\">\n<dt>intermolecular force<\/dt>\n<dd id=\"fs-idp135842976\">noncovalent attractive force between atoms, molecules, and\/or ions<\/dd>\n<\/dl>\n<dl id=\"fs-idp128571888\">\n<dt>polarizability<\/dt>\n<dd id=\"fs-idm53459296\">measure of the ability of a charge to distort a molecule\u2019s charge distribution (electron cloud)<\/dd>\n<\/dl>\n<dl id=\"fs-idm134093104\">\n<dt>van der Waals force<\/dt>\n<dd id=\"fs-idm67077760\">attractive or repulsive force between molecules, including dipole-dipole, dipole-induced dipole, and London dispersion forces; does not include forces due to covalent or ionic bonding, or the attraction between ions and molecules<\/dd>\n<\/dl>\n<\/div>\n","protected":false},"author":1392,"menu_order":2,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[48],"contributor":[],"license":[],"class_list":["post-617","chapter","type-chapter","status-publish","hentry","chapter-type-numberless"],"part":598,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters\/617","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/users\/1392"}],"version-history":[{"count":4,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters\/617\/revisions"}],"predecessor-version":[{"id":2145,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters\/617\/revisions\/2145"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/parts\/598"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters\/617\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/media?parent=617"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapter-type?post=617"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/contributor?post=617"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/license?post=617"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}