{"id":2443,"date":"2018-04-11T23:52:55","date_gmt":"2018-04-12T03:52:55","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/chapter\/electron-transfer-ionic-bonds\/"},"modified":"2018-06-23T00:06:01","modified_gmt":"2018-06-23T04:06:01","slug":"electron-transfer-ionic-bonds","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/chapter\/electron-transfer-ionic-bonds\/","title":{"raw":"9.4 Electron Transfer: Ionic Bonds","rendered":"9.4 Electron Transfer: Ionic Bonds"},"content":{"raw":"<div class=\"section\" id=\"ball-ch09_s02\" lang=\"en\">\r\n<div class=\"learning_objectives editable block\" id=\"ball-ch09_s02_n01\">\r\n<div class=\"bcc-box bcc-highlight\">\r\n<h3>Learning Objectives<\/h3>\r\nBy the end of this section, you will be able to:\r\n<ul>\r\n \t<li>State the octet rule.<\/li>\r\n \t<li>Define <em>ionic bond<\/em>.<\/li>\r\n \t<li>Demonstrate electron transfer between atoms to form ionic bonds.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n<p id=\"ball-ch09_s02_p01\" class=\"para editable block\">In <a class=\"xref\" href=\"ball-ch09_s01#ball-ch09_s01\">Section 8.3 \"Lewis Electron Dot Diagrams,\"<\/a>\u00a0we saw how ions are formed by losing electrons to make cations or by gaining electrons to form anions. The astute reader may have noticed something: Many of the ions that form have eight electrons in their valence shell. Either atoms gain enough electrons to have eight electrons in the valence shell and become the appropriately charged anion, or they lose the electrons in their original valence shell. The <em class=\"emphasis\">lower<\/em> shell, now the valence shell, has eight electrons in it, so the atom becomes positively charged. For whatever reason, having eight electrons in a valence shell is a particularly energetically stable arrangement of electrons. The trend that atoms like to have eight electrons in their valence shell is called the <em><span class=\"margin_term\"><a class=\"glossterm\">octet rule<\/a><\/span><\/em>. When atoms form compounds, the octet rule is not always satisfied for all atoms at all times, but it is a very good rule of thumb for understanding the kinds of bonding arrangements that atoms can make.<\/p>\r\n<p id=\"ball-ch09_s02_p02\" class=\"para editable block\">It is not impossible to violate the octet rule. Consider sodium: in its elemental form, it has one valence electron and is stable. It is rather reactive, however, and does not require a lot of energy to remove that electron to make the Na<sup class=\"superscript\">+<\/sup> ion. We <em class=\"emphasis\">could<\/em> remove another electron by adding even more energy to the ion, to make the Na<sup class=\"superscript\">2+<\/sup> ion. However, that requires much more energy than is normally available in chemical reactions, so sodium stops at a 1+\u00a0charge after losing a single electron. It turns out that the Na<sup class=\"superscript\">+<\/sup> ion has a complete octet in its new valence shell, the <em class=\"emphasis\">n<\/em> = 2 shell, which satisfies the octet rule. The octet rule is a result of trends in energies and is useful in explaining why atoms form the ions that they do.<\/p>\r\n<p id=\"ball-ch09_s02_p03\" class=\"para editable block\">Now consider an Na atom in the presence of a Cl atom. The two atoms have these Lewis electron dot diagrams and electron configurations:<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/NaCl-1.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/NaCl-1-1.png\" alt=\"NaCl-1\" width=\"400\" height=\"60\" class=\"wp-image-4387 aligncenter\" \/><\/a>For the Na atom to obtain an octet, it must lose an electron; for the Cl atom to gain an octet, it must gain an electron. An electron transfers from the Na atom to the Cl atom:<\/p>\r\n\r\n<div class=\"informalfigure large block\">\r\n<p class=\"para editable block\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/NaCl-2.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/NaCl-2-1.png\" alt=\"NaCl-2\" width=\"400\" height=\"60\" class=\"wp-image-4388 aligncenter\" \/><\/a>resulting in two ions\u2014the Na<sup class=\"superscript\">+<\/sup> ion and the Cl<sup class=\"superscript\">\u2212<\/sup> ion:<\/p>\r\n\r\n<div class=\"informalfigure large block\">\r\n<p class=\"para editable block\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/NaCl-3.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/NaCl-3-1.png\" alt=\"NaCl-3\" width=\"400\" height=\"70\" class=\"wp-image-4389 aligncenter\" \/><\/a>Both species now have complete octets, and the electron shells are energetically stable. From basic physics, we know that opposite charges attract. This is what happens to the Na<sup class=\"superscript\">+<\/sup> and Cl<sup class=\"superscript\">\u2212<\/sup> ions:<\/p>\r\n\r\n<div class=\"informalfigure large block\">\r\n<p class=\"para editable block\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/NaCl-4.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/NaCl-4-1.png\" alt=\"NaCl-4\" width=\"400\" height=\"40\" class=\"wp-image-4390 aligncenter\" \/><\/a>where we have written the final formula (the formula for sodium chloride) as per the convention for ionic compounds, without listing the charges explicitly. The attraction between oppositely charged ions is called an <em><span class=\"margin_term\"><a class=\"glossterm\">ionic bond<\/a><\/span><\/em>, and it is one of the main types of chemical bonds in chemistry. Ionic bonds are caused by electrons <em class=\"emphasis\">transferring<\/em> from one atom to another.<\/p>\r\n\r\n<div class=\"informalfigure large block\">\r\n<p id=\"ball-ch09_s02_p08\" class=\"para editable block\">In electron transfer, the number of electrons lost must equal the number of electrons gained. We saw this in the formation of NaCl. A similar process occurs between Mg atoms and O atoms, except in this case two electrons are transferred:<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/MgO-1.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/MgO-1-1.png\" alt=\"MgO-1\" width=\"400\" height=\"60\" class=\"wp-image-4385 aligncenter\" \/><\/a>The two ions each have octets as their valence shell, and the two oppositely charged particles attract, making an ionic bond:<\/p>\r\n\r\n<div class=\"informalfigure large block\">\r\n<p class=\"para editable block\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/MgO-2.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/MgO-2-1.png\" alt=\"MgO-2\" width=\"400\" height=\"40\" class=\"wp-image-4386 aligncenter\" \/><\/a>Remember, in the final formula for the ionic compound, we do not write the charges on the ions.<\/p>\r\n\r\n<div class=\"informalfigure large block\">\r\n<p id=\"ball-ch09_s02_p11\" class=\"para editable block\">What about when an Na atom interacts with an O atom? The O atom needs two electrons to complete its valence octet, but the Na atom supplies only one electron:<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/NaO-1.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/NaO-1-1.png\" alt=\"NaO-1\" width=\"400\" height=\"40\" class=\"wp-image-4391 aligncenter\" \/><\/a>The O atom still does not have an octet of electrons. What we need is a second Na atom to donate a second electron to the O atom:<\/p>\r\n\r\n<div class=\"informalfigure large block\">\r\n<p class=\"para editable block\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/NaO-2.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/NaO-2-1.png\" alt=\"NaO-2\" width=\"400\" height=\"70\" class=\"wp-image-4392 aligncenter\" \/><\/a>These three ions attract each other to give an overall neutral-charged ionic compound, which we write as Na<sub class=\"subscript\">2<\/sub>O. The need for the number of electrons lost being equal to the number of electrons gained explains why ionic compounds have the ratio of cations to anions that they do. This is required by the law of conservation of matter as well.<\/p>\r\n\r\n<div class=\"informalfigure large block\">\r\n<div class=\"textbox shaded\">\r\n<h3 class=\"title\">Example 1<\/h3>\r\n<p id=\"ball-ch09_s02_p14\" class=\"para\">With arrows, illustrate the transfer of electrons to form calcium chloride from Ca atoms and Cl atoms.<\/p>\r\n&nbsp;\r\n<p class=\"simpara\"><strong>Solution<\/strong><\/p>\r\n<p id=\"ball-ch09_s02_p15\" class=\"para\">A Ca atom has two valence electrons, while a Cl atom has seven electrons. A Cl atom needs only one more to complete its octet, while Ca atoms have two electrons to lose. Thus we need two Cl atoms to accept the two electrons from one Ca atom. The transfer process looks like this:<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/CaCl-1.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CaCl-1-1.png\" alt=\"CaCl-1\" width=\"400\" height=\"80\" class=\"wp-image-4382 aligncenter\" \/><\/a><span style=\"font-size: 1em\">The oppositely charged ions attract each other to make CaCl<\/span><sub class=\"subscript\">2<\/sub><span style=\"font-size: 1em\">.<\/span><\/p>\r\n\r\n<div class=\"informalfigure large\">\r\n\r\n&nbsp;\r\n<p class=\"simpara\"><strong><em class=\"emphasis bolditalic\">Test Yourself<\/em><\/strong><\/p>\r\n<p id=\"ball-ch09_s02_p17\" class=\"para\">With arrows, illustrate the transfer of electrons to form potassium sulfide from K atoms and S atoms.<\/p>\r\n&nbsp;\r\n<p class=\"simpara\"><strong><em class=\"emphasis\">Answer<\/em><\/strong><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/KS-1.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/KS-1-1.png\" alt=\"KS-1\" width=\"400\" height=\"80\" class=\"wp-image-4384 aligncenter\" \/><\/a><\/p>\r\n\r\n<div class=\"informalfigure large\"><\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"informalfigure large\">\r\n<p id=\"ball-ch09_s02_p18\" class=\"para editable block\">The strength of ionic bonding depends on two major characteristics: the magnitude of the charges and the size of the ion. The greater the magnitude of the charge, the stronger the ionic bond. The smaller the ion, the stronger the ionic bond (because a smaller ion size allows the ions to get closer together). The measured strength of ionic bonding is called the <em><span class=\"margin_term\"><a class=\"glossterm\">lattice energy<\/a><\/span><\/em>. Some lattice energies are given in <a class=\"xref\" href=\"#ball-ch09_s02_t01\">Table 1 \"Lattice Energies of Some Ionic Compounds.\"<\/a><\/p>\r\n\r\n<div class=\"table block\" id=\"ball-ch09_s02_t01\">\r\n<table style=\"border-spacing: 0px\" cellpadding=\"0\">\r\n<thead>\r\n<tr>\r\n<th>Compound<\/th>\r\n<th align=\"right\">Lattice Energy (kJ\/mol)<\/th>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr>\r\n<td>LiF<\/td>\r\n<td align=\"right\">1,036<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>LiCl<\/td>\r\n<td align=\"right\">853<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>NaCl<\/td>\r\n<td align=\"right\">786<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>NaBr<\/td>\r\n<td align=\"right\">747<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>MgF<sub class=\"subscript\">2<\/sub><\/td>\r\n<td align=\"right\">2,957<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>Na<sub class=\"subscript\">2<\/sub>O<\/td>\r\n<td align=\"right\">2,481<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>MgO<\/td>\r\n<td align=\"right\">3,791<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n<div class=\"callout block\" id=\"ball-ch09_s02_n03\">\r\n<p class=\"title\"><strong><span class=\"title-prefix\">Table 1.<\/span><\/strong> Lattice Energies of Some Ionic Compounds<\/p>\r\n\r\n<div class=\"textbox shaded\">\r\n<div class=\"callout block\" id=\"ball-ch09_s02_n03\">\r\n<h3 class=\"title\">Chemistry Is Everywhere: Salt<\/h3>\r\n<p id=\"ball-ch09_s02_p19\" class=\"para\">The element sodium (part [a] in the accompanying figure) is a very reactive metal; given the opportunity, it will react with the sweat on your hands and form sodium hydroxide, which is a very corrosive substance. The element chlorine (part [b] in the accompanying figure) is a pale yellow, corrosive gas that should not be inhaled due to its poisonous nature. Bring these two hazardous substances together, however, and they react to make the ionic compound sodium chloride (part [c] in the accompanying figure), known simply as salt.<\/p>\r\n\r\n<div class=\"figure medium\" id=\"ball-ch09_s02_f01\">\r\n<div class=\"copyright\">\r\n\r\n[caption id=\"attachment_3230\" align=\"aligncenter\" width=\"400\"]<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/07\/element.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/element-1024x477-1.png\" alt=\"element\" class=\"wp-image-3230\" height=\"187\" width=\"400\" \/><\/a> <strong>Figure 1.<\/strong> Sodium +\u00a0Chlorine = Sodium Chloride \u00a0(a) Sodium is a very reactive metal. (b) Chlorine is a pale yellow, noxious gas. (c) Together, sodium and chlorine make sodium chloride\u2014salt\u2014which is necessary for our survival.[\/caption]\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<p class=\"para\">Salt is necessary for life. Na<sup class=\"superscript\">+<\/sup> ions are one of the main ions in the human body and are necessary to regulate the fluid balance in the body. Cl<sup class=\"superscript\">\u2212<\/sup> ions are necessary for proper nerve function and respiration. Both of these ions are supplied by salt. The taste of salt is one of the fundamental tastes; salt is probably the most ancient flavouring known, and one of the few rocks we eat.<\/p>\r\n<p id=\"ball-ch09_s02_p22\" class=\"para\">The health effects of too much salt are still under debate, although a 2010 report by the US Department of Agriculture concluded that \u201cexcessive sodium intake\u2026raises blood pressure, a well-accepted and extraordinarily common risk factor for stroke, coronary heart disease, and kidney disease.\u201d<span class=\"footnote\" id=\"fwk-ball-fn09_001\"><a class=\"link\" href=\"http:\/\/www.cnpp.usda.gov\/DGAs2010-DGACReport.htm\" target=\"_blank\" rel=\"noopener\">[footnote]US Department of Agriculture Committee for Nutrition Policy and Promotion, \u201cReport of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans,\u201d accessed January 5, 2010, http:\/\/www.cnpp.usda.gov\/DGAs2010-DGACReport.htm[\/footnote]<\/a><\/span> It is clear that most people ingest more salt than their bodies need, and most nutritionists recommend curbing salt intake. Curiously, people who suffer from low salt (called <em class=\"emphasis\">hyponatria<\/em>) do so not because they ingest too little salt but because they drink too much water. Endurance athletes and others involved in extended strenuous exercise need to watch their water intake so their body\u2019s salt content is not diluted to dangerous levels.<\/p>\r\n\r\n<\/div>\r\n<h2>Key Concepts and Summary<\/h2>\r\nThe tendency to form species that have eight electrons in the valence shell is called the octet rule. \u00a0The attraction of oppositely charged ions caused by electron transfer is called an ionic bond. \u00a0\u00a0The strength of ionic bonding depends on the magnitude of the charges and the sizes of the ions.\r\n\r\n<\/div>\r\n<\/div>\r\n<div class=\"key_takeaways editable block\" id=\"ball-ch09_s02_n04\">\r\n<div class=\"bcc-box bcc-info\">\r\n<h3>Exercises<\/h3>\r\n<div class=\"qandaset block\" id=\"ball-ch09_s02_qs01\">\r\n<div class=\"question\">\r\n\r\n1. Comment on the possible formation of the K<sup class=\"superscript\">2+<\/sup> ion. Why is its formation unlikely?\r\n\r\n<span style=\"font-size: 1em\">2. How many electrons does a Ba atom have to lose to have a complete octet in its valence shell?<\/span>\r\n\r\n<span style=\"font-size: 1em\">3. How many electrons does an Se atom have to gain to have a complete octet in its valence shell?<\/span>\r\n\r\n<span style=\"font-size: 1em\">4. With arrows, illustrate the transfer of electrons to form potassium chloride from K atoms and Cl atoms.<\/span>\r\n\r\n<span style=\"font-size: 1em\">5. With arrows, illustrate the transfer of electrons to form scandium fluoride from Sc atoms and F atoms.<\/span>\r\n\r\n<span style=\"font-size: 1em\">6. Which ionic compound has the higher lattice energy\u2014KI or MgO? Why?\u00a0<\/span>\r\n\r\n<span style=\"font-size: 1em\">7. Which ionic compound has the higher lattice energy\u2014BaS or MgO? Why?<\/span>\r\n<p id=\"ball-ch09_s02_qs01_p23\" class=\"para\"><\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<b>Answers<\/b>\r\n\r\n1. The K<sup class=\"superscript\">2+<\/sup> ion is unlikely to form because the K<sup class=\"superscript\">+<\/sup> ion already satisfies the octet rule and is rather stable.\r\n\r\n<span style=\"font-size: 1em\">2. two<\/span>\r\n\r\n<span style=\"font-size: 1em\">3. two<\/span>\r\n\r\n4.<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/KCl-1.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/KCl-1-1.png\" alt=\"KCl-1\" width=\"400\" height=\"49\" class=\"wp-image-4383 aligncenter\" \/><\/a>5.<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/ScF-1.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/ScF-1-1.png\" alt=\"ScF-1\" width=\"400\" height=\"94\" class=\"wp-image-4393 aligncenter\" \/><\/a>6. MgO because the ions have a higher magnitude charge\r\n\r\n7. MgO because the ions are smaller\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>","rendered":"<div class=\"section\" id=\"ball-ch09_s02\" lang=\"en\">\n<div class=\"learning_objectives editable block\" id=\"ball-ch09_s02_n01\">\n<div class=\"bcc-box bcc-highlight\">\n<h3>Learning Objectives<\/h3>\n<p>By the end of this section, you will be able to:<\/p>\n<ul>\n<li>State the octet rule.<\/li>\n<li>Define <em>ionic bond<\/em>.<\/li>\n<li>Demonstrate electron transfer between atoms to form ionic bonds.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<p id=\"ball-ch09_s02_p01\" class=\"para editable block\">In <a class=\"xref\" href=\"ball-ch09_s01#ball-ch09_s01\">Section 8.3 &#8220;Lewis Electron Dot Diagrams,&#8221;<\/a>\u00a0we saw how ions are formed by losing electrons to make cations or by gaining electrons to form anions. The astute reader may have noticed something: Many of the ions that form have eight electrons in their valence shell. Either atoms gain enough electrons to have eight electrons in the valence shell and become the appropriately charged anion, or they lose the electrons in their original valence shell. The <em class=\"emphasis\">lower<\/em> shell, now the valence shell, has eight electrons in it, so the atom becomes positively charged. For whatever reason, having eight electrons in a valence shell is a particularly energetically stable arrangement of electrons. The trend that atoms like to have eight electrons in their valence shell is called the <em><span class=\"margin_term\"><a class=\"glossterm\">octet rule<\/a><\/span><\/em>. When atoms form compounds, the octet rule is not always satisfied for all atoms at all times, but it is a very good rule of thumb for understanding the kinds of bonding arrangements that atoms can make.<\/p>\n<p id=\"ball-ch09_s02_p02\" class=\"para editable block\">It is not impossible to violate the octet rule. Consider sodium: in its elemental form, it has one valence electron and is stable. It is rather reactive, however, and does not require a lot of energy to remove that electron to make the Na<sup class=\"superscript\">+<\/sup> ion. We <em class=\"emphasis\">could<\/em> remove another electron by adding even more energy to the ion, to make the Na<sup class=\"superscript\">2+<\/sup> ion. However, that requires much more energy than is normally available in chemical reactions, so sodium stops at a 1+\u00a0charge after losing a single electron. It turns out that the Na<sup class=\"superscript\">+<\/sup> ion has a complete octet in its new valence shell, the <em class=\"emphasis\">n<\/em> = 2 shell, which satisfies the octet rule. The octet rule is a result of trends in energies and is useful in explaining why atoms form the ions that they do.<\/p>\n<p id=\"ball-ch09_s02_p03\" class=\"para editable block\">Now consider an Na atom in the presence of a Cl atom. The two atoms have these Lewis electron dot diagrams and electron configurations:<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/NaCl-1.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/NaCl-1-1.png\" alt=\"NaCl-1\" width=\"400\" height=\"60\" class=\"wp-image-4387 aligncenter\" \/><\/a>For the Na atom to obtain an octet, it must lose an electron; for the Cl atom to gain an octet, it must gain an electron. An electron transfers from the Na atom to the Cl atom:<\/p>\n<div class=\"informalfigure large block\">\n<p class=\"para editable block\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/NaCl-2.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/NaCl-2-1.png\" alt=\"NaCl-2\" width=\"400\" height=\"60\" class=\"wp-image-4388 aligncenter\" \/><\/a>resulting in two ions\u2014the Na<sup class=\"superscript\">+<\/sup> ion and the Cl<sup class=\"superscript\">\u2212<\/sup> ion:<\/p>\n<div class=\"informalfigure large block\">\n<p class=\"para editable block\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/NaCl-3.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/NaCl-3-1.png\" alt=\"NaCl-3\" width=\"400\" height=\"70\" class=\"wp-image-4389 aligncenter\" \/><\/a>Both species now have complete octets, and the electron shells are energetically stable. From basic physics, we know that opposite charges attract. This is what happens to the Na<sup class=\"superscript\">+<\/sup> and Cl<sup class=\"superscript\">\u2212<\/sup> ions:<\/p>\n<div class=\"informalfigure large block\">\n<p class=\"para editable block\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/NaCl-4.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/NaCl-4-1.png\" alt=\"NaCl-4\" width=\"400\" height=\"40\" class=\"wp-image-4390 aligncenter\" \/><\/a>where we have written the final formula (the formula for sodium chloride) as per the convention for ionic compounds, without listing the charges explicitly. The attraction between oppositely charged ions is called an <em><span class=\"margin_term\"><a class=\"glossterm\">ionic bond<\/a><\/span><\/em>, and it is one of the main types of chemical bonds in chemistry. Ionic bonds are caused by electrons <em class=\"emphasis\">transferring<\/em> from one atom to another.<\/p>\n<div class=\"informalfigure large block\">\n<p id=\"ball-ch09_s02_p08\" class=\"para editable block\">In electron transfer, the number of electrons lost must equal the number of electrons gained. We saw this in the formation of NaCl. A similar process occurs between Mg atoms and O atoms, except in this case two electrons are transferred:<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/MgO-1.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/MgO-1-1.png\" alt=\"MgO-1\" width=\"400\" height=\"60\" class=\"wp-image-4385 aligncenter\" \/><\/a>The two ions each have octets as their valence shell, and the two oppositely charged particles attract, making an ionic bond:<\/p>\n<div class=\"informalfigure large block\">\n<p class=\"para editable block\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/MgO-2.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/MgO-2-1.png\" alt=\"MgO-2\" width=\"400\" height=\"40\" class=\"wp-image-4386 aligncenter\" \/><\/a>Remember, in the final formula for the ionic compound, we do not write the charges on the ions.<\/p>\n<div class=\"informalfigure large block\">\n<p id=\"ball-ch09_s02_p11\" class=\"para editable block\">What about when an Na atom interacts with an O atom? The O atom needs two electrons to complete its valence octet, but the Na atom supplies only one electron:<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/NaO-1.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/NaO-1-1.png\" alt=\"NaO-1\" width=\"400\" height=\"40\" class=\"wp-image-4391 aligncenter\" \/><\/a>The O atom still does not have an octet of electrons. What we need is a second Na atom to donate a second electron to the O atom:<\/p>\n<div class=\"informalfigure large block\">\n<p class=\"para editable block\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/NaO-2.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/NaO-2-1.png\" alt=\"NaO-2\" width=\"400\" height=\"70\" class=\"wp-image-4392 aligncenter\" \/><\/a>These three ions attract each other to give an overall neutral-charged ionic compound, which we write as Na<sub class=\"subscript\">2<\/sub>O. The need for the number of electrons lost being equal to the number of electrons gained explains why ionic compounds have the ratio of cations to anions that they do. This is required by the law of conservation of matter as well.<\/p>\n<div class=\"informalfigure large block\">\n<div class=\"textbox shaded\">\n<h3 class=\"title\">Example 1<\/h3>\n<p id=\"ball-ch09_s02_p14\" class=\"para\">With arrows, illustrate the transfer of electrons to form calcium chloride from Ca atoms and Cl atoms.<\/p>\n<p>&nbsp;<\/p>\n<p class=\"simpara\"><strong>Solution<\/strong><\/p>\n<p id=\"ball-ch09_s02_p15\" class=\"para\">A Ca atom has two valence electrons, while a Cl atom has seven electrons. A Cl atom needs only one more to complete its octet, while Ca atoms have two electrons to lose. Thus we need two Cl atoms to accept the two electrons from one Ca atom. The transfer process looks like this:<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/CaCl-1.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CaCl-1-1.png\" alt=\"CaCl-1\" width=\"400\" height=\"80\" class=\"wp-image-4382 aligncenter\" \/><\/a><span style=\"font-size: 1em\">The oppositely charged ions attract each other to make CaCl<\/span><sub class=\"subscript\">2<\/sub><span style=\"font-size: 1em\">.<\/span><\/p>\n<div class=\"informalfigure large\">\n<p>&nbsp;<\/p>\n<p class=\"simpara\"><strong><em class=\"emphasis bolditalic\">Test Yourself<\/em><\/strong><\/p>\n<p id=\"ball-ch09_s02_p17\" class=\"para\">With arrows, illustrate the transfer of electrons to form potassium sulfide from K atoms and S atoms.<\/p>\n<p>&nbsp;<\/p>\n<p class=\"simpara\"><strong><em class=\"emphasis\">Answer<\/em><\/strong><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/KS-1.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/KS-1-1.png\" alt=\"KS-1\" width=\"400\" height=\"80\" class=\"wp-image-4384 aligncenter\" \/><\/a><\/p>\n<div class=\"informalfigure large\"><\/div>\n<\/div>\n<\/div>\n<div class=\"informalfigure large\">\n<p id=\"ball-ch09_s02_p18\" class=\"para editable block\">The strength of ionic bonding depends on two major characteristics: the magnitude of the charges and the size of the ion. The greater the magnitude of the charge, the stronger the ionic bond. The smaller the ion, the stronger the ionic bond (because a smaller ion size allows the ions to get closer together). The measured strength of ionic bonding is called the <em><span class=\"margin_term\"><a class=\"glossterm\">lattice energy<\/a><\/span><\/em>. Some lattice energies are given in <a class=\"xref\" href=\"#ball-ch09_s02_t01\">Table 1 &#8220;Lattice Energies of Some Ionic Compounds.&#8221;<\/a><\/p>\n<div class=\"table block\" id=\"ball-ch09_s02_t01\">\n<table style=\"border-spacing: 0px\" cellpadding=\"0\">\n<thead>\n<tr>\n<th>Compound<\/th>\n<th align=\"right\">Lattice Energy (kJ\/mol)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>LiF<\/td>\n<td align=\"right\">1,036<\/td>\n<\/tr>\n<tr>\n<td>LiCl<\/td>\n<td align=\"right\">853<\/td>\n<\/tr>\n<tr>\n<td>NaCl<\/td>\n<td align=\"right\">786<\/td>\n<\/tr>\n<tr>\n<td>NaBr<\/td>\n<td align=\"right\">747<\/td>\n<\/tr>\n<tr>\n<td>MgF<sub class=\"subscript\">2<\/sub><\/td>\n<td align=\"right\">2,957<\/td>\n<\/tr>\n<tr>\n<td>Na<sub class=\"subscript\">2<\/sub>O<\/td>\n<td align=\"right\">2,481<\/td>\n<\/tr>\n<tr>\n<td>MgO<\/td>\n<td align=\"right\">3,791<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<div class=\"callout block\" id=\"ball-ch09_s02_n03\">\n<p class=\"title\"><strong><span class=\"title-prefix\">Table 1.<\/span><\/strong> Lattice Energies of Some Ionic Compounds<\/p>\n<div class=\"textbox shaded\">\n<div class=\"callout block\" id=\"ball-ch09_s02_n03\">\n<h3 class=\"title\">Chemistry Is Everywhere: Salt<\/h3>\n<p id=\"ball-ch09_s02_p19\" class=\"para\">The element sodium (part [a] in the accompanying figure) is a very reactive metal; given the opportunity, it will react with the sweat on your hands and form sodium hydroxide, which is a very corrosive substance. The element chlorine (part [b] in the accompanying figure) is a pale yellow, corrosive gas that should not be inhaled due to its poisonous nature. Bring these two hazardous substances together, however, and they react to make the ionic compound sodium chloride (part [c] in the accompanying figure), known simply as salt.<\/p>\n<div class=\"figure medium\" id=\"ball-ch09_s02_f01\">\n<div class=\"copyright\">\n<figure id=\"attachment_3230\" aria-describedby=\"caption-attachment-3230\" style=\"width: 400px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/07\/element.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/element-1024x477-1.png\" alt=\"element\" class=\"wp-image-3230\" height=\"187\" width=\"400\" \/><\/a><figcaption id=\"caption-attachment-3230\" class=\"wp-caption-text\"><strong>Figure 1.<\/strong> Sodium +\u00a0Chlorine = Sodium Chloride \u00a0(a) Sodium is a very reactive metal. (b) Chlorine is a pale yellow, noxious gas. (c) Together, sodium and chlorine make sodium chloride\u2014salt\u2014which is necessary for our survival.<\/figcaption><\/figure>\n<\/div>\n<\/div>\n<\/div>\n<p class=\"para\">Salt is necessary for life. Na<sup class=\"superscript\">+<\/sup> ions are one of the main ions in the human body and are necessary to regulate the fluid balance in the body. Cl<sup class=\"superscript\">\u2212<\/sup> ions are necessary for proper nerve function and respiration. Both of these ions are supplied by salt. The taste of salt is one of the fundamental tastes; salt is probably the most ancient flavouring known, and one of the few rocks we eat.<\/p>\n<p id=\"ball-ch09_s02_p22\" class=\"para\">The health effects of too much salt are still under debate, although a 2010 report by the US Department of Agriculture concluded that \u201cexcessive sodium intake\u2026raises blood pressure, a well-accepted and extraordinarily common risk factor for stroke, coronary heart disease, and kidney disease.\u201d<span class=\"footnote\" id=\"fwk-ball-fn09_001\"><a class=\"link\" href=\"http:\/\/www.cnpp.usda.gov\/DGAs2010-DGACReport.htm\" target=\"_blank\" rel=\"noopener\"><a class=\"footnote\" title=\"US Department of Agriculture Committee for Nutrition Policy and Promotion, \u201cReport of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans,\u201d accessed January 5, 2010, http:\/\/www.cnpp.usda.gov\/DGAs2010-DGACReport.htm\" id=\"return-footnote-2443-1\" href=\"#footnote-2443-1\" aria-label=\"Footnote 1\"><sup class=\"footnote\">[1]<\/sup><\/a><\/a><\/span> It is clear that most people ingest more salt than their bodies need, and most nutritionists recommend curbing salt intake. Curiously, people who suffer from low salt (called <em class=\"emphasis\">hyponatria<\/em>) do so not because they ingest too little salt but because they drink too much water. Endurance athletes and others involved in extended strenuous exercise need to watch their water intake so their body\u2019s salt content is not diluted to dangerous levels.<\/p>\n<\/div>\n<h2>Key Concepts and Summary<\/h2>\n<p>The tendency to form species that have eight electrons in the valence shell is called the octet rule. \u00a0The attraction of oppositely charged ions caused by electron transfer is called an ionic bond. \u00a0\u00a0The strength of ionic bonding depends on the magnitude of the charges and the sizes of the ions.<\/p>\n<\/div>\n<\/div>\n<div class=\"key_takeaways editable block\" id=\"ball-ch09_s02_n04\">\n<div class=\"bcc-box bcc-info\">\n<h3>Exercises<\/h3>\n<div class=\"qandaset block\" id=\"ball-ch09_s02_qs01\">\n<div class=\"question\">\n<p>1. Comment on the possible formation of the K<sup class=\"superscript\">2+<\/sup> ion. Why is its formation unlikely?<\/p>\n<p><span style=\"font-size: 1em\">2. How many electrons does a Ba atom have to lose to have a complete octet in its valence shell?<\/span><\/p>\n<p><span style=\"font-size: 1em\">3. How many electrons does an Se atom have to gain to have a complete octet in its valence shell?<\/span><\/p>\n<p><span style=\"font-size: 1em\">4. With arrows, illustrate the transfer of electrons to form potassium chloride from K atoms and Cl atoms.<\/span><\/p>\n<p><span style=\"font-size: 1em\">5. With arrows, illustrate the transfer of electrons to form scandium fluoride from Sc atoms and F atoms.<\/span><\/p>\n<p><span style=\"font-size: 1em\">6. Which ionic compound has the higher lattice energy\u2014KI or MgO? Why?\u00a0<\/span><\/p>\n<p><span style=\"font-size: 1em\">7. Which ionic compound has the higher lattice energy\u2014BaS or MgO? Why?<\/span><\/p>\n<p id=\"ball-ch09_s02_qs01_p23\" class=\"para\">\n<\/div>\n<\/div>\n<p><b>Answers<\/b><\/p>\n<p>1. The K<sup class=\"superscript\">2+<\/sup> ion is unlikely to form because the K<sup class=\"superscript\">+<\/sup> ion already satisfies the octet rule and is rather stable.<\/p>\n<p><span style=\"font-size: 1em\">2. two<\/span><\/p>\n<p><span style=\"font-size: 1em\">3. two<\/span><\/p>\n<p>4.<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/KCl-1.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/KCl-1-1.png\" alt=\"KCl-1\" width=\"400\" height=\"49\" class=\"wp-image-4383 aligncenter\" \/><\/a>5.<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/ScF-1.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/ScF-1-1.png\" alt=\"ScF-1\" width=\"400\" height=\"94\" class=\"wp-image-4393 aligncenter\" \/><\/a>6. MgO because the ions have a higher magnitude charge<\/p>\n<p>7. MgO because the ions are smaller<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<hr class=\"before-footnotes clear\" \/><div class=\"footnotes\"><ol><li id=\"footnote-2443-1\">US Department of Agriculture Committee for Nutrition Policy and Promotion, \u201cReport of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans,\u201d accessed January 5, 2010, http:\/\/www.cnpp.usda.gov\/DGAs2010-DGACReport.htm <a href=\"#return-footnote-2443-1\" class=\"return-footnote\" aria-label=\"Return to footnote 1\">&crarr;<\/a><\/li><\/ol><\/div>","protected":false},"author":330,"menu_order":5,"template":"","meta":{"pb_show_title":"on","pb_short_title":"9.4 Electron Transfer: Ionic Bonds","pb_subtitle":"","pb_authors":[],"pb_section_license":"cc-by-nc-sa"},"chapter-type":[],"contributor":[],"license":[54],"class_list":["post-2443","chapter","type-chapter","status-publish","hentry","license-cc-by-nc-sa"],"part":1538,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-json\/pressbooks\/v2\/chapters\/2443","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-json\/wp\/v2\/users\/330"}],"version-history":[{"count":10,"href":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-json\/pressbooks\/v2\/chapters\/2443\/revisions"}],"predecessor-version":[{"id":4706,"href":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-json\/pressbooks\/v2\/chapters\/2443\/revisions\/4706"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-json\/pressbooks\/v2\/parts\/1538"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-json\/pressbooks\/v2\/chapters\/2443\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-json\/wp\/v2\/media?parent=2443"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-json\/pressbooks\/v2\/chapter-type?post=2443"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-json\/wp\/v2\/contributor?post=2443"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-json\/wp\/v2\/license?post=2443"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}