{"id":1316,"date":"2018-04-11T22:51:20","date_gmt":"2018-04-12T02:51:20","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/chapter\/2-3-atomic-structure-and-symbolism\/"},"modified":"2019-06-11T17:25:18","modified_gmt":"2019-06-11T21:25:18","slug":"2-3-atomic-structure-and-symbolism","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/chapter\/2-3-atomic-structure-and-symbolism\/","title":{"raw":"3.3 Atomic Structure and Symbolism","rendered":"3.3 Atomic Structure and Symbolism"},"content":{"raw":"<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>Write and interpret symbols that depict the atomic number, mass number, and charge of an atom or ion<\/li>\r\n \t<li>Define the atomic mass unit and average atomic mass<\/li>\r\n \t<li>Calculate average atomic mass and isotopic abundance<\/li>\r\n<\/ul>\r\n<\/div>\r\n<p id=\"fs-idp188136384\">The development of modern atomic theory revealed much about the inner structure of atoms. It was learned that an atom contains a very small nucleus composed of positively charged protons and uncharged neutrons, surrounded by a much larger volume of space containing negatively charged electrons. The nucleus contains the majority of an atom\u2019s mass because protons and neutrons are much heavier than electrons, whereas electrons occupy almost all of an atom\u2019s volume. The diameter of an atom is on the order of 10<sup>\u221210<\/sup> m, whereas the diameter of the nucleus is roughly 10<sup>\u221215<\/sup> m\u2014about 100,000 times smaller. For a perspective about their relative sizes, consider this: If the nucleus were the size of a blueberry, the atom would be about the size of a football stadium (<a href=\"#CNX_Chem_02_03_AtomSize\" class=\"autogenerated-content\">Figure 1<\/a>).<\/p>\r\n\r\n<figure id=\"CNX_Chem_02_03_AtomSize\"><figcaption>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"1300\"]<a href=\"https:\/\/opentextbc.ca\/chemistry\/wp-content\/uploads\/sites\/150\/2016\/05\/CNX_Chem_02_03_AtomSize.jpg\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CNX_Chem_02_03_AtomSize-2.jpg\" alt=\"The diagram on the left shows a picture of an atom that is 10 to the negative tenth power meters in diameter. The nucleus is labeled at the center of the atom and is 10 to the negative fifteenth power meters. The central figure shows a photograph of an American football stadium. The figure on the right shows a photograph of a person with a handful of blueberries.\" width=\"1300\" height=\"400\" \/><\/a> <strong>Figure 1.<\/strong> If an atom could be expanded to the size of a football stadium, the nucleus would be the size of a single blueberry. (credit middle: modification of work by \u201cbabyknight\u201d\/Wikimedia Commons; credit right: modification of work by Paxson Woelber)[\/caption]\r\n\r\n<\/figcaption><\/figure>\r\n<p id=\"fs-idm171776576\">Atoms\u2014and the protons, neutrons, and electrons that compose them\u2014are extremely small. For example, a carbon atom weighs less than 2 \u00d7 10<sup>\u221223<\/sup> g, and an electron has a charge of less than 2 \u00d7 10<sup>\u221219<\/sup> C (coulomb). When describing the properties of tiny objects such as atoms, we use appropriately small units of measure, such as the <strong>atomic mass unit (amu)<\/strong> and the <strong>fundamental unit of charge (e)<\/strong>. The amu was originally defined based on hydrogen, the lightest element, then later in terms of oxygen. Since 1961, it has been defined with regard to the most abundant isotope of carbon, atoms of which are assigned masses of exactly 12 amu. (This isotope is known as \u201ccarbon-12\u201d as will be discussed later in this module.) Thus, one amu is exactly $latex \\frac{1}{12} $ of the mass of one carbon-12 atom: 1 amu = 1.6605 \u00d7 10<sup>\u221224<\/sup> g. (The <strong>Dalton (Da)<\/strong> and the <strong>unified atomic mass unit (u)<\/strong> are alternative units that are equivalent to the amu.) The fundamental unit of charge (also called the elementary charge) equals the magnitude of the charge of an electron (e) with e = 1.602 \u00d7 10<sup>\u221219<\/sup> C.<\/p>\r\n<p id=\"fs-idm166273840\">A proton has a mass of 1.0073 amu and a charge of 1+. A neutron is a slightly heavier particle with a mass 1.0087 amu and a charge of zero; as its name suggests, it is neutral. The electron has a charge of 1\u2212 and is a much lighter particle with a mass of about 0.00055 amu (it would take about 1800 electrons to equal the mass of one proton. The properties of these fundamental particles are summarized in <a href=\"#fs-idp90857696\" class=\"autogenerated-content\">Table 1<\/a>. (An observant student might notice that the sum of an atom\u2019s subatomic particles does not equal the atom\u2019s actual mass: The total mass of six protons, six neutrons, and six electrons is 12.0993 amu, slightly larger than 12.00 amu. This \u201cmissing\u201d mass is known as the mass defect, and you will learn about it in the chapter on nuclear chemistry.)<\/p>\r\n<p id=\"fs-idp27048016\">The number of protons in the nucleus of an atom is its <strong>atomic number (Z)<\/strong>. This is the defining trait of an element: Its value determines the identity of the atom. For example, any atom that contains six protons is the element carbon and has the atomic number 6, regardless of how many neutrons or electrons it may have. A neutral atom must contain the same number of positive and negative charges, so the number of protons equals the number of electrons. Therefore, the atomic number also indicates the number of electrons in an atom. The total number of protons and neutrons in an atom is called its <strong>mass number (A)<\/strong>. The number of neutrons is therefore the difference between the mass number and the atomic number: A \u2013 Z = number of neutrons.<\/p>\r\n<p style=\"text-align: center\">$latex \\begin{array}{r @ {{}={}} l} \\text{atomic number (Z)} &amp; \\text{number of protons} \\\\[1em] \\text{mass number (A)} &amp; \\text{number of protons + number of neutrons} \\\\[1em] \\text{A - Z} &amp; \\text{number of neutrons} \\end{array}$<\/p>\r\n\r\n<table id=\"fs-idp90857696\" class=\"span-all\" summary=\"This table gives the name, location, charge in C, unit charge, mass in A M U and mass in grams for electrons, protons and neutrons. Electrons are located outside of the nucleus, have a charge of negative 1.602 times 10 to the negative nineteenth power, a unit charge of negative 1, and a mass of 0.00055 A M U or 0.00091 times 10 to the negative twenty-fourth power grams. Protons are located within the nucleus, have a charge of 1.602 times 10 to the negative nineteenth power, have a unit charge of positive 1, and have a mass of 1.0073 A M U or 1.6726 times 10 to the negative twenty-fourth power grams. Neutrons are located within the nucleus, have a charge of 0, have a unit charge of 0, and have a mass of 1.0087 A M U or 1.6749 times 10 to the negative twenty-fourth power grams.\">\r\n<thead>\r\n<tr valign=\"top\">\r\n<th>Name<\/th>\r\n<th>Location<\/th>\r\n<th>Charge (C)<\/th>\r\n<th>Unit Charge<\/th>\r\n<th>Mass (amu)<\/th>\r\n<th>Mass (g)<\/th>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr valign=\"top\">\r\n<td>electron<\/td>\r\n<td>outside nucleus<\/td>\r\n<td>\u22121.602 \u00d7 10<sup>\u221219<\/sup><\/td>\r\n<td>1\u2212<\/td>\r\n<td>0.00055<\/td>\r\n<td>0.00091 \u00d7 10<sup>\u221224<\/sup><\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>proton<\/td>\r\n<td>nucleus<\/td>\r\n<td>1.602 \u00d7 10<sup>\u221219<\/sup><\/td>\r\n<td>1+<\/td>\r\n<td>1.00727<\/td>\r\n<td>1.67262 \u00d7 10<sup>\u221224<\/sup><\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>neutron<\/td>\r\n<td>nucleus<\/td>\r\n<td>0<\/td>\r\n<td>0<\/td>\r\n<td>1.00866<\/td>\r\n<td>1.67493 \u00d7 10<sup>\u221224<\/sup><\/td>\r\n<\/tr>\r\n<tr>\r\n<td colspan=\"6\"><strong>Table 1.<\/strong> Properties of Subatomic Particles<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<p id=\"fs-idm159569776\">Atoms are electrically neutral if they contain the same number of positively charged protons and negatively charged electrons. When the numbers of these subatomic particles are <em>not<\/em> equal, the atom is electrically charged and is called an <strong>ion<\/strong>. The charge of an atom is defined as follows:<\/p>\r\n<p id=\"fs-idp142952368\">Atomic charge = number of protons \u2212 number of electrons<\/p>\r\n<p id=\"fs-idp59351760\">As will be discussed in more detail later in this chapter, atoms (and molecules) typically acquire charge by gaining or losing electrons. An atom that gains one or more electrons will exhibit a negative charge and is called an <strong>anion<\/strong>. Positively charged atoms called <strong>cations<\/strong> are formed when an atom loses one or more electrons. For example, a neutral sodium atom (Z = 11) has 11 electrons. If this atom loses one electron, it will become a cation with a 1+ charge (11 \u2212 10 = 1+). A neutral oxygen atom (Z = 8) has eight electrons, and if it gains two electrons it will become an anion with a 2\u2212 charge (8 \u2212 10 = 2\u2212).<\/p>\r\n\r\n<div class=\"textbox shaded\" id=\"fs-idm5511728\">\r\n<h3>Example 1<\/h3>\r\n<p id=\"fs-idm54131248\">Iodine is an essential trace element in our diet; it is needed to produce thyroid hormone. Insufficient iodine in the diet can lead to the development of a goiter, an enlargement of the thyroid gland (<a href=\"#CNX_Chem_02_03_Iodine\" class=\"autogenerated-content\">Figure 2<\/a>).<\/p>\r\n\r\n<figure id=\"CNX_Chem_02_03_Iodine\"><figcaption>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"975\"]<a href=\"https:\/\/opentextbc.ca\/chemistry\/wp-content\/uploads\/sites\/150\/2016\/05\/CNX_Chem_02_03_Iodine.jpg\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CNX_Chem_02_03_Iodine-2.jpg\" alt=\"Figure A shows a photo of a person who has a very swollen thyroid in his or her neck. Figure B shows a photo of a canister of iodized salt.\" width=\"975\" height=\"432\" \/><\/a> <strong>Figure 2.<\/strong> (a) Insufficient iodine in the diet can cause an enlargement of the thyroid gland called a goiter. (b) The addition of small amounts of iodine to salt, which prevents the formation of goiters, has helped eliminate this concern in the US where salt consumption is high. (credit a: modification of work by \u201cAlmazi\u201d\/Wikimedia Commons; credit b: modification of work by Mike Mozart)[\/caption]\r\n\r\n<\/figcaption><\/figure>\r\n<p id=\"fs-idm90509824\">The addition of small amounts of iodine to table salt (iodized salt) has essentially eliminated this health concern in the United States, but as much as 40% of the world\u2019s population is still at risk of iodine deficiency. The iodine atoms are added as anions, and each has a 1\u2212 charge and a mass number of 127. Determine the numbers of protons, neutrons, and electrons in one of these iodine anions.<\/p>\r\n&nbsp;\r\n<p id=\"fs-idp104898720\"><strong>Solution<\/strong><\/p>\r\nThe atomic number of iodine (53) tells us that a neutral iodine atom contains 53 protons in its nucleus and 53 electrons outside its nucleus. Because the sum of the numbers of protons and neutrons equals the mass number, 127, the number of neutrons is 74 (127 \u2212 53 = 74). Since the iodine is added as a 1\u2212 anion, the number of electrons is 54 [53 \u2013 (1\u2013) = 54].\r\n\r\n&nbsp;\r\n\r\n<em><strong>Test Yourself<\/strong><\/em>\r\n\r\nAn ion of platinum has a mass number of 195 and contains 74 electrons. How many protons and neutrons does it contain, and what is its charge?\r\n\r\n&nbsp;\r\n\r\n<strong><em>Answers<\/em><\/strong>\r\n\r\n78 protons; 117 neutrons; charge is 4+\r\n\r\n<\/div>\r\n<section id=\"fs-idm176092496\">\r\n<div class=\"textbox shaded\">\r\n<h3 class=\"title\">Example 2<\/h3>\r\n<ol id=\"ball-ch03_s01_l03\" class=\"orderedlist\">\r\n \t<li>The most common carbon atoms have six protons and six neutrons in their nuclei. What are the atomic number and the mass number of these carbon atoms?<\/li>\r\n \t<li>An isotope of uranium has an atomic number of 92 and a mass number of 235. What are the number of protons and neutrons in the nucleus of this atom?<\/li>\r\n<\/ol>\r\n&nbsp;\r\n<p class=\"simpara\"><strong>Solution<\/strong><\/p>\r\n\r\n<ol id=\"ball-ch03_s01_l04\" class=\"orderedlist\">\r\n \t<li>If a carbon atom has six protons in its nucleus, its atomic number is 6. If it also has six neutrons in the nucleus, then the mass number is 6 +\u00a06, or 12.<\/li>\r\n \t<li>If the atomic number of uranium is 92, then that is the number of protons in the nucleus. Because the mass number is 235, then the number of neutrons in the nucleus is 235 \u2212 92, or 143.<\/li>\r\n<\/ol>\r\n&nbsp;\r\n<p class=\"simpara\"><strong><em class=\"emphasis bolditalic\">Test Yourself<\/em><\/strong><\/p>\r\n<p id=\"ball-ch03_s01_p09\" class=\"para\">The number of protons in the nucleus of a tin atom is 50, while the number of neutrons in the nucleus is 68. What are the atomic number and the mass number of this isotope?<\/p>\r\n&nbsp;\r\n<p class=\"simpara\"><strong><em class=\"emphasis\">Answer<\/em><\/strong><\/p>\r\n<p id=\"ball-ch03_s01_p10\" class=\"para\">Atomic number = 50, mass number = 118<\/p>\r\n\r\n<\/div>\r\n<h2>Chemical Symbols<\/h2>\r\n<p id=\"fs-idm48306304\">A <strong>chemical symbol<\/strong> is an abbreviation that we use to indicate an element or an atom of an element. For example, the symbol for mercury is Hg (<a href=\"#CNX_Chem_02_03_SiSymbol\" class=\"autogenerated-content\">Figure 3<\/a>). We use the same symbol to indicate one atom of mercury (microscopic domain) or to label a container of many atoms of the element mercury (macroscopic domain).<\/p>\r\n\r\n<figure id=\"CNX_Chem_02_03_SiSymbol\">\r\n\r\n[caption id=\"attachment_1312\" align=\"aligncenter\" width=\"200\"]<a href=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CNX_Chem_02_03_SiSymbol-2-e1528932573783.jpg\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CNX_Chem_02_03_SiSymbol-2-e1528932573783.jpg\" alt=\"\" width=\"200\" height=\"160\" class=\"wp-image-1312 size-full\" \/><\/a> <strong>Figure 3.<\/strong> The symbol Hg represents the element mercury regardless of the amount; it could represent one atom of mercury or a large amount of mercury.[\/caption]<\/figure>\r\nThe symbols for several common elements and their atoms are listed in <a href=\"#fs-idm36686800\" class=\"autogenerated-content\">Table 2<\/a>. Some symbols are derived from the common name of the element; others are abbreviations of the name in another language. Most symbols have one or two letters, but three-letter symbols have been used to describe some elements that have atomic numbers greater than 112. To avoid confusion with other notations, only the first letter of a symbol is capitalized. For example, Co is the symbol for the element cobalt, but CO is the notation for the compound carbon monoxide, which contains atoms of the elements carbon (C) and oxygen (O). All known elements and their symbols are in the periodic table in <a href=\"https:\/\/opentextbc.ca\/chemistry\/chapter\/2-5-the-periodic-table\/#CNX_Chem_02_05_PerTable1\" class=\"autogenerated-content\" target=\"_blank\" rel=\"noopener\">Figure 2 in Chapter 3.5 The Periodic Table<\/a> (also found in <a href=\"https:\/\/opentextbc.ca\/chemistry\/back-matter\/the-periodic-table\/\" class=\"autogenerated-content\" target=\"_blank\" rel=\"noopener\">Appendix A<\/a>).\r\n<table id=\"fs-idm36686800\" class=\"span-all\" summary=\"This table has two columns labeled element and symbol. The first letter of the symbol is always an uppercase letter while the second letter of the symbol is always a lowercase letter. Aluminum has the symbol A L. Bromine has the symbol B R, calcium has the symbol C A, carbon has the symbol C, chlorine has the symbol C L, chromium has the symbol C R, cobalt has the symbol C O, copper has the symbol C U, from cuprum, fluorine has the symbol F, gold has the symbol A U, from aurum, helium has the symbol H E, hydrogen has the symbol H, iodine has the symbol I, iron has the symbol F E, from ferrum, lead has the symbol P B, from plumbum, magnesium has the symbol M G, mercury has the symbol H G from hydrargyrum, nitrogen has the symbol N, oxygen has the symbol O, potassium has the symbol K, from kalium, silicon has the symbol S I, silver has the symbol A G, from argentum, sodium has the symbol N A from natrium, sulfur has the symbol S, tin has the symbol S N from stannum, and zinc has the symbol Z N.\">\r\n<thead>\r\n<tr valign=\"top\">\r\n<th>Element<\/th>\r\n<th>Symbol<\/th>\r\n<th>Element<\/th>\r\n<th>Symbol<\/th>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr valign=\"top\">\r\n<td>aluminum<\/td>\r\n<td>Al<\/td>\r\n<td>iron<\/td>\r\n<td>Fe (from <em>ferrum<\/em>)<\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>bromine<\/td>\r\n<td>Br<\/td>\r\n<td>lead<\/td>\r\n<td>Pb (from <em>plumbum<\/em>)<\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>calcium<\/td>\r\n<td>Ca<\/td>\r\n<td>magnesium<\/td>\r\n<td>Mg<\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>carbon<\/td>\r\n<td>C<\/td>\r\n<td>mercury<\/td>\r\n<td>Hg (from <em>hydrargyrum<\/em>)<\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>chlorine<\/td>\r\n<td>Cl<\/td>\r\n<td>nitrogen<\/td>\r\n<td>N<\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>chromium<\/td>\r\n<td>Cr<\/td>\r\n<td>oxygen<\/td>\r\n<td>O<\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>cobalt<\/td>\r\n<td>Co<\/td>\r\n<td>potassium<\/td>\r\n<td>K (from <em>kalium<\/em>)<\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>copper<\/td>\r\n<td>Cu (from <em>cuprum<\/em>)<\/td>\r\n<td>silicon<\/td>\r\n<td>Si<\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>fluorine<\/td>\r\n<td>F<\/td>\r\n<td>silver<\/td>\r\n<td>Ag (from<em> argentum<\/em>)<\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>gold<\/td>\r\n<td>Au (from <em>aurum<\/em>)<\/td>\r\n<td>sodium<\/td>\r\n<td>Na (from <em>natrium<\/em>)<\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>helium<\/td>\r\n<td>He<\/td>\r\n<td>sulfur<\/td>\r\n<td>S<\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>hydrogen<\/td>\r\n<td>H<\/td>\r\n<td>tin<\/td>\r\n<td>Sn (from <em>stannum<\/em>)<\/td>\r\n<\/tr>\r\n<tr valign=\"top\">\r\n<td>iodine<\/td>\r\n<td>I<\/td>\r\n<td>zinc<\/td>\r\n<td>Zn<\/td>\r\n<\/tr>\r\n<tr>\r\n<td colspan=\"4\"><strong>Table 2.<\/strong> Some Common Elements and Their Symbols<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<p id=\"fs-idm105035264\">Traditionally, the discoverer (or discoverers) of a new element names the element. However, until the name is recognized by the International Union of Pure and Applied Chemistry (IUPAC), the recommended name of the new element is based on the Latin word(s) for its atomic number. For example, element 106 was called unnilhexium (Unh), element 107 was called unnilseptium (Uns), and element 108 was called unniloctium (Uno) for several years. These elements are now named after scientists (or occasionally locations); for example, element 106 is now known as <em>seaborgium<\/em> (Sg) in honor of Glenn Seaborg, a Nobel Prize winner who was active in the discovery of several heavy elements.<\/p>\r\n\r\n<div id=\"fs-idm111013376\" class=\"textbox shaded\">\r\n\r\n<img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/OSC_Interactive_200-1-2.png\" alt=\"\u00a0\" width=\"119\" height=\"74\" class=\"alignleft\" \/>\r\n<p id=\"fs-idm3892928\">Visit this <a href=\"http:\/\/openstaxcollege.org\/l\/16IUPAC\">site<\/a> to learn more about IUPAC, the International Union of Pure and Applied Chemistry, and explore its periodic table.<\/p>\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/section><section id=\"fs-idp42149200\">\r\n<h2>Isotopes<\/h2>\r\n<p id=\"fs-idm240748912\">The symbol for a specific isotope of any element is written by placing the mass number as a superscript to the left of the element symbol (<a href=\"#CNX_Chem_02_03_AtomSym\" class=\"autogenerated-content\">Figure 4<\/a>). The atomic number is sometimes written as a subscript preceding the symbol, but since this number defines the element\u2019s identity, as does its symbol, it is often omitted. For example, magnesium exists as a mixture of three isotopes, each with an atomic number of 12 and with mass numbers of 24, 25, and 26, respectively. These isotopes can be identified as <sup>24<\/sup>Mg, <sup>25<\/sup>Mg, and <sup>26<\/sup>Mg. These isotope symbols are read as \u201celement, mass number\u201d and can be symbolized consistent with this reading. For instance, <sup>24<\/sup>Mg is read as \u201cmagnesium 24,\u201d and can be written as \u201cmagnesium-24\u201d or \u201cMg-24.\u201d <sup>25<\/sup>Mg is read as \u201cmagnesium 25,\u201d and can be written as \u201cmagnesium-25\u201d or \u201cMg-25.\u201d All magnesium atoms have 12 protons in their nucleus. They differ only because a <sup>24<\/sup>Mg atom has 12 neutrons in its nucleus, a <sup>25<\/sup>Mg atom has 13 neutrons, and a <sup>26<\/sup>Mg has 14 neutrons. \u00a0Therefore the masses of isotopes of an element, <strong>isotopic mass<\/strong>, differ - see Table 3.<\/p>\r\n&nbsp;\r\n<figure id=\"CNX_Chem_02_03_AtomSym\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"492\"]<a href=\"https:\/\/opentextbc.ca\/chemistry\/wp-content\/uploads\/sites\/150\/2016\/05\/CNX_Chem_02_03_AtomSym.jpg\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CNX_Chem_02_03_AtomSym-2.jpg\" alt=\"This diagram shows the symbol for helium, \u201cH e.\u201d The number to the upper left of the symbol is the mass number, which is 4. The number to the upper right of the symbol is the charge which is positive 2. The number to the lower left of the symbol is the atomic number, which is 2. This number is often omitted. Also shown is \u201cM g\u201d which stands for magnesium It has a mass number of 24, a charge of positive 2, and an atomic number of 12.\" width=\"492\" height=\"109\" class=\"\" \/><\/a> <strong>Figure 4.<\/strong> The symbol for an atom indicates the element via its usual two-letter symbol, the mass number as a left superscript, the atomic number as a left subscript (sometimes omitted), and the charge as a right superscript.[\/caption]<\/figure>\r\n<p id=\"fs-idm198096624\">Information about the naturally occurring isotopes of elements with atomic numbers 1 through 10 is given in <a href=\"#fs-idm87646592\" class=\"autogenerated-content\">Table 3<\/a>. Note that in addition to standard names and symbols, the isotopes of hydrogen are often referred to using common names and accompanying symbols. Hydrogen-2, symbolized <sup>2<\/sup>H, is also called deuterium and sometimes symbolized D. Hydrogen-3, symbolized <sup>3<\/sup>H, is also called tritium and sometimes symbolized T.<\/p>\r\n\r\n<table id=\"fs-idm87646592\" class=\"span-all\" style=\"width: 513px;height: 1429px\" summary=\"This table has seven columns labeled element, symbol, atomic number, number of protons, number of neutrons, mass in A M U, and percent natural abundance. The symbols for each element each show the mass number in the upper left and the atomic number in the lower left. Therefore hydrogen left superscript 1, left subscript 1, or protium, has a mass number of 1 and an atomic number of 1. Protium has one proton, 0 neutrons, a mass of 1.0078 and a natural abundance percentage of 99.985. Hydrogen left superscript 2, left subscript 1, or deuterium, has an atomic number of 1, 1 proton, 1 neutron, a mass of 2.0141 and a natural abundance percentage of 0.015. Hydrogen left superscript 3, left subscript 1, or tritium, has an atomic number of 11 protons, 2 neutrons, and a mass of 3.01605. No natural abundance percentage is given. Helium left superscript 3, left subscript 2 has an atomic number of 2, 2 protons, 1 neutron, a mass of 3.01603, and a natural abundance percentage of 0.00013. Helium left superscript 4, left subscript 2 has an atomic number of 2, 2 protons, 2 neutrons, a mass of 4.0026 and a natural abundance percentage of 100. Lithium left superscript 6, left subscript 3 has an atomic number of 3, 3 protons, 3 neutrons, a mass of 6.0151, and a natural abundance percentage of 7.42. Lithium left superscript 7, left subscript 3 has an atomic number of 3, 3 protons, 4 neutrons, a mass of 7.0160, and a natural abundance percentage of 92.8. Beryllium left superscript 9, left subscript 4 has an atomic number of 4, 4 protons, 5 neutrons, a mass of 9.0122, and a natural abundance percentage of 100. Boron left superscript 10, left subscript 5 has an atomic number of 5, 5 protons, 5 neutrons and a natural abundance percentage of 19.9. Boron left superscript 11, left subscript 5 has an atomic number of 5, 5 protons, 6 neutrons, a mass of 11.0093 and a natural abundance of 80.1. Carbon left superscript 12, left subscript 6 has an atomic number of 6, 6 protons, 6 neutrons, a mass of 12, and a natural abundance percentage of 98.89. Carbon left superscript 13, left subscript 6 has an atomic number of 6, 6 protons, 7 neutrons, a mass of 13.0033, and a natural abundance percentage of 1.11. Carbon left superscript 14, left subscript 6 has an atomic number of 6, 6 protons, 8 neutrons, and a mass of 14.0032. Its natural abundance percentage is not reported. Nitrogen left superscript 14, left subscript 7 has an atomic number of 7, 7 protons, 7 neutrons, a mass of 14.0031, and a natural abundance percentage of 99.63. Nitrogen left superscript 15, left subscript 7 has an atomic number of 7, 7 protons, 8 neutrons, a mass of 15.0001, and a natural abundance percentage of 0.37. Oxygen left superscript 16, left subscript 8 has an atomic number of 8, 8 protons, 8 neutrons, a mass of 15.9949, and a natural abundance percentage of 99.759. Oxygen left superscript 17, left subscript 8 has an atomic number of 8, 8 protons, 9 neutrons, a mass of 16.9991, and a natural abundance percentage of 0.037. Oxygen left superscript 18, left subscript 8 has an atomic number of 8, 8 protons, 10 neutrons, a mass of 17.9992, and a natural abundance percentage of 0.204. Fluorine left superscript 19, left subscript 9 has an atomic number of 9, 9 protons, 10 neutrons, a mass of 18.9984, and a natural abundance percentage of 100. Neon left superscript 20, left subscript 10 has an atomic number of 10, 10 protons, 10 neutrons, a mass of 19.9924, and a natural abundance percentage of 90.92. Neon left superscript 21, left subscript 10 has an atomic number of 10, 10 protons, 11 neutrons, a mass of 20.994, and a natural abundance percentage of 0.257. Neon left superscript 22, left subscript 10 has an atomic number of 10, 10 protons, 12 neutrons, a mass of 21.9914, and a natural abundance percentage of 8.82.\">\r\n<thead>\r\n<tr style=\"height: 72px\" valign=\"top\">\r\n<th style=\"width: 62.21875px;height: 72px\">Element<\/th>\r\n<th style=\"width: 148.6875px;height: 72px\">Symbol<\/th>\r\n<th style=\"width: 46.21875px;height: 72px\"><sup>Atomic Number<\/sup><\/th>\r\n<th style=\"width: 43.109375px;height: 72px\"><sup># of Protons<\/sup><\/th>\r\n<th style=\"width: 51.046875px;height: 72px\"><sup># of Neutrons<\/sup><\/th>\r\n<th style=\"width: 54.234375px;height: 72px\">Isotopic Mass (amu)<\/th>\r\n<th style=\"width: 78.25px;height: 72px;text-align: left\">% Natural Abundance<\/th>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr style=\"height: 136px\" valign=\"middle\">\r\n<td style=\"width: 62.21875px;text-align: center;height: 408px\" rowspan=\"3\">hydrogen<\/td>\r\n<td style=\"width: 148.6875px;text-align: center;height: 136px\">$latex _1^1\\text{H}$\r\n<div><\/div>\r\n(protium)<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 136px\">1<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 136px\">1<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 136px\">0<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 136px\">1.0078<\/td>\r\n<td style=\"width: 78.25px;height: 136px;text-align: left\">99.989<\/td>\r\n<\/tr>\r\n<tr style=\"height: 136px\" valign=\"top\">\r\n<td style=\"width: 148.6875px;text-align: center;height: 136px\">$latex _1^2\\text{H}$\r\n<div><\/div>\r\n(deuterium)<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 136px\">1<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 136px\">1<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 136px\">1<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 136px\">2.0141<\/td>\r\n<td style=\"width: 78.25px;height: 136px;text-align: left\">0.0115<\/td>\r\n<\/tr>\r\n<tr style=\"height: 136px\" valign=\"top\">\r\n<td style=\"width: 148.6875px;text-align: center;height: 136px\">$latex _1^3\\text{H}$\r\n<div><\/div>\r\n(tritium)<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 136px\">1<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 136px\">1<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 136px\">2<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 136px\">3.01605<\/td>\r\n<td style=\"width: 78.25px;height: 136px;text-align: left\">\u2014 (trace)<\/td>\r\n<\/tr>\r\n<tr style=\"height: 24px\" valign=\"middle\">\r\n<td style=\"width: 62.21875px;text-align: center;height: 48px\" rowspan=\"2\">helium<\/td>\r\n<td style=\"width: 148.6875px;text-align: center;height: 24px\">$latex _2^3\\text{He}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 24px\">2<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 24px\">2<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 24px\">1<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 24px\">3.01603<\/td>\r\n<td style=\"width: 78.25px;height: 24px;text-align: left\">0.00013<\/td>\r\n<\/tr>\r\n<tr style=\"height: 24px\" valign=\"top\">\r\n<td style=\"width: 148.6875px;text-align: center;height: 24px\">$latex _2^4\\text{He}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 24px\">2<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 24px\">2<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 24px\">2<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 24px\">4.0026<\/td>\r\n<td style=\"width: 78.25px;height: 24px;text-align: left\">100<\/td>\r\n<\/tr>\r\n<tr style=\"height: 24px\" valign=\"middle\">\r\n<td style=\"width: 62.21875px;text-align: center;height: 48px\" rowspan=\"2\">lithium<\/td>\r\n<td style=\"width: 148.6875px;text-align: center;height: 24px\">$latex _3^6\\text{Li}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 24px\">3<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 24px\">3<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 24px\">3<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 24px\">6.0151<\/td>\r\n<td style=\"width: 78.25px;height: 24px;text-align: left\">7.59<\/td>\r\n<\/tr>\r\n<tr style=\"height: 24px\" valign=\"top\">\r\n<td style=\"width: 148.6875px;text-align: center;height: 24px\">$latex _3^7\\text{Li}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 24px\">3<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 24px\">3<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 24px\">4<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 24px\">7.0160<\/td>\r\n<td style=\"width: 78.25px;height: 24px;text-align: left\">92.41<\/td>\r\n<\/tr>\r\n<tr style=\"height: 24px\" valign=\"top\">\r\n<td style=\"width: 62.21875px;text-align: center;height: 24px\">beryllium<\/td>\r\n<td style=\"width: 148.6875px;text-align: center;height: 24px\">$latex _4^9\\text{Be}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 24px\">4<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 24px\">4<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 24px\">5<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 24px\">9.0122<\/td>\r\n<td style=\"width: 78.25px;height: 24px;text-align: left\">100<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"middle\">\r\n<td style=\"width: 62.21875px;text-align: center;height: 96px\" rowspan=\"2\">boron<\/td>\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _5^{10}\\text{B}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">5<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">5<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">5<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">10.0129<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">19.9<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"top\">\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _5^{11}\\text{B}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">5<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">5<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">6<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">11.0093<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">80.1<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"middle\">\r\n<td style=\"width: 62.21875px;text-align: center;height: 144px\" rowspan=\"3\">carbon<\/td>\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _6^{12}\\text{C}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">6<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">6<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">6<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">12.0000<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">98.89<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"middle\">\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _6^{13}\\text{C}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">6<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">6<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">7<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">13.0034<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">1.11<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"top\">\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _6^{14}\\text{C}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">6<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">6<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">8<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">14.0032<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">\u2014 (trace)<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"middle\">\r\n<td style=\"width: 62.21875px;text-align: center;height: 96px\" rowspan=\"2\">nitrogen<\/td>\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _7^{14}\\text{N}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">7<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">7<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">7<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">14.0031<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">99.63<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"middle\">\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _7^{15}\\text{N}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">7<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">7<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">8<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">15.0001<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">0.37<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"middle\">\r\n<td style=\"width: 62.21875px;text-align: center;height: 144px\" rowspan=\"3\">oxygen<\/td>\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _8^{16}\\text{O}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">8<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">8<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">8<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">15.9949<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">99.757<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"middle\">\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _8^{17}\\text{O}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">8<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">8<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">9<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">16.9991<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">0.038<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"middle\">\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _8^{18}\\text{O}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">8<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">8<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">10<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">17.9992<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">0.205<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"middle\">\r\n<td style=\"width: 62.21875px;text-align: center;height: 48px\">fluorine<\/td>\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _9^{19}\\text{F}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">9<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">9<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">10<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">18.9984<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">100<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"middle\">\r\n<td style=\"width: 62.21875px;text-align: center;height: 144px\" rowspan=\"3\">neon<\/td>\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _{10}^{20}\\text{Ne}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">10<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">10<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">10<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">19.9924<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">90.48<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"middle\">\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _{10}^{21}\\text{Ne}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">10<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">10<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">11<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">20.9938<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">0.27<\/td>\r\n<\/tr>\r\n<tr style=\"height: 48px\" valign=\"middle\">\r\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">$latex _{10}^{22}\\text{Ne}$<\/td>\r\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">10<\/td>\r\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">10<\/td>\r\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">12<\/td>\r\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">21.9914<\/td>\r\n<td style=\"width: 78.25px;height: 48px;text-align: left\">9.25<\/td>\r\n<\/tr>\r\n<tr style=\"height: 24px\">\r\n<td style=\"width: 519.765625px;height: 24px\" colspan=\"7\"><strong>Table 3.\u00a0<\/strong>Nuclear Compositions of Atoms of the Very Light Elements<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<div class=\"textbox shaded\">\r\n<h3 class=\"title\">Example 3<\/h3>\r\n<ol id=\"ball-ch03_s01_l05\" class=\"orderedlist\">\r\n \t<li>What is the symbol for an isotope of uranium that has an atomic number of 92 and a mass number of 235?<\/li>\r\n \t<li>How many protons and neutrons are in $latex _{26}^{56}\\text{Fe}$?<\/li>\r\n<\/ol>\r\n&nbsp;\r\n<p class=\"simpara\"><strong>Solution<\/strong><\/p>\r\n\r\n<ol id=\"ball-ch03_s01_l06\" class=\"orderedlist\">\r\n \t<li>The symbol for this isotope is\u00a0$latex _{92}^{235}\\text{U}$.<\/li>\r\n \t<li>This iron atom has 26 protons and 56 \u2212 26 = 30 neutrons.<\/li>\r\n<\/ol>\r\n&nbsp;\r\n<p class=\"simpara\"><strong><em class=\"emphasis bolditalic\">Test Yourself<\/em><\/strong><\/p>\r\n<p id=\"ball-ch03_s01_p16\" class=\"para\">How many protons are in $latex _{23}^{11}\\text{Na}$?<\/p>\r\n&nbsp;\r\n<p class=\"simpara\"><strong><em class=\"emphasis\">Answer<\/em><\/strong><\/p>\r\n<p id=\"ball-ch03_s01_p17\" class=\"para\">11 protons<\/p>\r\n\r\n<\/div>\r\n<\/section><section id=\"fs-idp42149200\">\r\n<div class=\"textbox shaded\">\r\n<h3 class=\"title\">Example 4<\/h3>\r\n<p class=\"Indent\"><span>Determine the number of protons, neutrons and electrons for the ion: <\/span><\/p>\r\n<p class=\"Indent\"><span>\u00a0<img width=\"27\" height=\"24\" \/><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/Screen-Shot-2018-05-03-at-12.54.51-PM.png\" alt=\"\" width=\"63\" height=\"49\" class=\"alignnone size-full wp-image-3379\" \/><\/span><\/p>\r\n<p class=\"Solution\"><strong>Solution\u00a0\u00a0 <\/strong><\/p>\r\n<p class=\"Indent\">The atomic number is 17, thus the ion contains 17 protons. The mass number is 35, therefore it contains 35 \u2013 17 = 18 neutrons. Because it is negatively charged (-1), it must have one more electron as compared to protons, thus 17 + 1 = 18 electrons.<\/p>\r\n&nbsp;\r\n<p class=\"SelfTest\"><strong>Test Yourself<\/strong><\/p>\r\n<p class=\"Indent\">Determine the number of electrons in each of the following ions. Hint: Use the periodic table to first determine the number of protons based on its elemental identity. \u00a0\u00a0a)<span>\u00a0 <\/span>Mg<sup>2+<\/sup><span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/span>b) Fe<sup>3+<\/sup><span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/span>c) O<sup>2-<\/sup><\/p>\r\n&nbsp;\r\n<p class=\"Answers\"><em><strong>Answers<\/strong><\/em><\/p>\r\n<p class=\"Answers\">a) 10<span>\u00a0\u00a0\u00a0 <\/span>b) 23<span>\u00a0\u00a0\u00a0<\/span>c) 10<\/p>\r\n\r\n<\/div>\r\n<\/section><section id=\"fs-idp42149200\">\r\n<div class=\"textbox shaded\">\r\n<h3 class=\"title\">Example 5<\/h3>\r\n<p class=\"Indent\">Determine the number of protons, neutrons and electrons for the following atom, as well as its identity (chemical symbol) for: <span><img width=\"28\" height=\"24\" \/><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/Screen-Shot-2018-05-03-at-12.53.17-PM.png\" alt=\"\" width=\"62\" height=\"46\" class=\"alignnone size-full wp-image-3378\" \/><\/span><\/p>\r\n&nbsp;\r\n<p class=\"Solution\"><strong>Solution<\/strong><span><strong>\u00a0\u00a0<\/strong> <\/span><\/p>\r\n<p class=\"Indent\">The atomic number is 92 and mass number is 238. From the atomic number 92 we know that this must be Uranium (chemical symbol = U). The atomic number is equal to the number of protons, thus the number of protons is 92. Because the mass number is equal to the sum of the protons and neutrons, we know that n + 92 = 238. Thus, the number of neutrons is 238 \u2013 92 = 146. Finally, the given symbol must represent an atom, not an ion (no electric charge is shown) and any atom is neutral, thus the number of electrons must be the same as the number of protons, or 92 .<\/p>\r\n&nbsp;\r\n<p class=\"SelfTest\"><em><strong>Test Yourself<\/strong><\/em><\/p>\r\n<p class=\"Indentpoints\">a)<span>\u00a0 <\/span>Write the complete atomic symbol for krypton, which contains 48 neutrons\/<\/p>\r\n<p class=\"Indentpoints\">b)<span>\u00a0 <\/span>How many protons, neutrons and electrons are in <sup>132<\/sup>Cs?<\/p>\r\n&nbsp;\r\n<p class=\"Answers\"><em><strong>Answers<\/strong><\/em><\/p>\r\n<p class=\"Answers\">a) <sup>84<\/sup>Kr<span>\u00a0 <\/span>b) protons = 55, neutrons = 77, electrons = 55<\/p>\r\n\r\n<\/div>\r\n<\/section><section id=\"fs-idp42149200\">\r\n<div id=\"fs-idm166072560\" class=\"textbox shaded\">\r\n\r\n<img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/OSC_Interactive_200-1-2.png\" alt=\"\u00a0\" width=\"122\" height=\"76\" class=\"alignleft\" \/>\r\n<p id=\"fs-idm243168608\">Use this <a href=\"http:\/\/openstaxcollege.org\/l\/16PhetAtomBld\">Build an Atom simulator<\/a> to build atoms of the first 10 elements, see which isotopes exist, check nuclear stability, and gain experience with isotope symbols.<\/p>\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/section><section id=\"fs-idm54315440\">\r\n<h2>Atomic Mass<\/h2>\r\n<p id=\"fs-idp64485984\">Because each proton and each neutron contribute approximately one amu to the mass of an atom, and each electron contributes far less, the <strong>atomic mass<\/strong> of a single atom is approximately equal to its mass number (a whole number). However, the average masses of atoms of most elements are not whole numbers because most elements exist naturally as mixtures of two or more isotopes.<\/p>\r\n<p id=\"fs-idp249209552\">The mass of an element shown in a periodic table or listed in a table of atomic masses is a weighted, average mass of all the isotopes present in a naturally occurring sample of that element. This is equal to the sum of each individual isotope\u2019s mass multiplied by its fractional abundance.<\/p>\r\n\r\n<div class=\"equation\" id=\"fs-idm56955264\" style=\"text-align: center\">$latex \\displaystyle{} \\text{average mass} = \\sum_{i} (\\text{fractional abundance} \\times \\text{isotopic mass})_{i} $<\/div>\r\n<p id=\"fs-idp53715664\">For example, the element boron is composed of two isotopes: About 19.9% of all boron atoms are <sup>10<\/sup>B with a mass of 10.0129 amu, and the remaining 80.1% are <sup>11<\/sup>B with a mass of 11.0093 amu. The average atomic mass for boron is calculated to be:<\/p>\r\n\r\n<div class=\"equation\" id=\"fs-idp64426960\" style=\"text-align: center\">$latex \\begin{array}{r @{{}={}} l} \\text{boron average mass} &amp; (0.199 \\times 10.0129 \\;\\text{amu}) + (0.801 \\times 11.0093 \\;\\text{amu}) \\\\[1em] &amp; 1.99 \\;\\text{amu} + 8.82 \\;\\text{amu} \\\\[1em] &amp; 10.81 \\;\\text{amu} \\end{array}$<\/div>\r\n<p id=\"fs-idm114336768\">It is important to understand that no single boron atom weighs exactly 10.8 amu; 10.8 amu is the average mass of all boron atoms, and individual boron atoms weigh either approximately 10 amu or 11 amu.<\/p>\r\n\r\n<div class=\"textbox shaded\" id=\"fs-idm139194256\">\r\n<h3>Example 6<\/h3>\r\n<p id=\"fs-idm202281808\">A meteorite found in central Indiana contains traces of the noble gas neon picked up from the solar wind during the meteorite\u2019s trip through the solar system. Analysis of a sample of the gas showed that it consisted of 91.84% <sup>20<\/sup>Ne (mass 19.9924 amu), 0.47% <sup>21<\/sup>Ne (mass 20.9940 amu), and 7.69% <sup>22<\/sup>Ne (mass 21.9914 amu). What is the average mass of the neon in the solar wind?<\/p>\r\n&nbsp;\r\n<p id=\"fs-idm194071296\"><strong>Solution<\/strong><\/p>\r\n\r\n<div class=\"equation\" id=\"fs-idm73306928\" style=\"text-align: center\">$latex \\begin{array}{r @{{}={}} l} \\text{average mass} &amp; (0.9184 \\times 19.9924 \\;\\text{amu}) + (0.0047 \\times 20.9940 \\;\\text{amu})+(0.0769 \\times 21.9914 \\;\\text{amu}) \\\\[1em] &amp; (18.36+0.099+1.69) \\;\\text{amu} \\\\[1em] &amp; 20.15 \\;\\text{amu} \\end{array}$<\/div>\r\n<p id=\"fs-idm3186256\">The average mass of a neon atom in the solar wind is 20.15 amu. (The average mass of a terrestrial neon atom is 20.1796 amu. This result demonstrates that we may find slight differences in the natural abundance of isotopes, depending on their origin.)<\/p>\r\n&nbsp;\r\n<p id=\"fs-idm187119072\"><em><strong>Test Yourself<\/strong><\/em>\r\nA sample of magnesium is found to contain 78.70% of <sup>24<\/sup>Mg atoms (mass 23.98 amu), 10.13% of <sup>25<\/sup>Mg atoms (mass 24.99 amu), and 11.17% of <sup>26<\/sup>Mg atoms (mass 25.98 amu). Calculate the average mass of a Mg atom.<\/p>\r\n&nbsp;\r\n\r\n<em><strong>Answer<\/strong><\/em>\r\n\r\n24.31 amu\r\n\r\n<\/div>\r\nWe can also do variations of this type of calculation, as shown in the next example.\r\n<div class=\"textbox shaded\" id=\"fs-idm233489360\">\r\n<h3>Example 7<\/h3>\r\n<p id=\"fs-idm170542656\">Naturally occurring chlorine consists of <sup>35<\/sup>Cl (mass 34.96885 amu) and <sup>37<\/sup>Cl (mass 36.96590 amu), with an average mass of 35.453 amu. What is the percent composition of Cl in terms of these two isotopes?<\/p>\r\n&nbsp;\r\n<p id=\"fs-idm111544320\"><strong>Solution<\/strong>\r\nThe average mass of chlorine is the fraction that is <sup>35<\/sup>Cl times the mass of <sup>35<\/sup>Cl plus the fraction that is <sup>37<\/sup>Cl times the mass of <sup>37<\/sup>Cl.<\/p>\r\n\r\n<div class=\"equation\" id=\"fs-idp1748832\" style=\"text-align: center\">$latex \\text{average mass} = (\\text{fraction of} \\ ^{35}\\text{Cl} \\ \\times \\ \\text{mass of} \\ ^{35}\\text{Cl}) + (\\text{fraction of} \\ ^{37}\\text{Cl} \\ \\times \\ \\text{mass of} \\ ^{37}\\text{Cl}) $<\/div>\r\n<p id=\"fs-idp35897648\">If we let <em>x<\/em> represent the fraction that is <sup>35<\/sup>Cl, then the fraction that is <sup>37<\/sup>Cl is represented by 1.00 \u2212 <em>x<\/em>.<\/p>\r\n<p id=\"fs-idm78207296\">(The fraction that is <sup>35<\/sup>Cl + the fraction that is <sup>37<\/sup>Cl must add up to 1, so the fraction of <sup>37<\/sup>Cl must equal 1.00 \u2212 the fraction of <sup>35<\/sup>Cl.)<\/p>\r\n<p id=\"fs-idm174110736\">Substituting this into the average mass equation, we have:<\/p>\r\n\r\n<div class=\"equation\" id=\"fs-idm50612880\" style=\"text-align: center\">$latex \\begin{array}{r @{{}={}} l}35.453 \\;\\text{amu} &amp; (x \\times 34.96885 \\;\\text{amu}) + [(1.00 - x) \\times 36.96590\\;\\text{amu}] \\\\[1em] 35.453 &amp; 34.96885x + 36.96590 - 36.96590x \\\\[1em] 1.99705x &amp; 1.513 \\\\[1em] x &amp; \\frac{1.513}{1.99705} = 0.7576 \\end{array}$<\/div>\r\n<p id=\"fs-idm84424288\">So solving yields: <em>x<\/em> = 0.7576, which means that 1.00 \u2212 0.7576 = 0.2424. Therefore, chlorine consists of 75.76% <sup>35<\/sup>Cl and 24.24% <sup>37<\/sup>Cl.<\/p>\r\n&nbsp;\r\n<p id=\"fs-idm140620960\"><em><b>Test Yourself<\/b><\/em><\/p>\r\nNaturally occurring copper consists of <sup>63<\/sup>Cu (mass 62.9296 amu) and <sup>65<\/sup>Cu (mass 64.9278 amu), with an average mass of 63.546 amu. What is the percent composition of Cu in terms of these two isotopes?\r\n\r\n<em><strong>Answers<\/strong><\/em>\r\n\r\n69.15% Cu-63 and 30.85% Cu-65\r\n\r\n<\/div>\r\n<div id=\"fs-idm186474352\" class=\"textbox shaded\">\r\n\r\n<span id=\"fs-idm183783632\"> <img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/OSC_Interactive_200-1-2.png\" alt=\"\u00a0\" width=\"111\" height=\"69\" class=\"alignleft\" \/><\/span>\r\n<p id=\"fs-idp99251296\">Visit this <a href=\"http:\/\/openstaxcollege.org\/l\/16PhetAtomMass\">site<\/a> to make mixtures of the main isotopes of the first 18 elements, gain experience with average atomic mass, and check naturally occurring isotope ratios using the Isotopes and Atomic Mass simulation.<\/p>\r\n\r\n<\/div>\r\n<p id=\"fs-idp64386064\">The occurrence and natural abundances of isotopes can be experimentally determined using an instrument called a mass spectrometer. Mass spectrometry (MS) is widely used in chemistry, forensics, medicine, environmental science, and many other fields to analyze and help identify the substances in a sample of material. In a typical mass spectrometer (<a href=\"#CNX_Chem_02_03_MassSpec\" class=\"autogenerated-content\">Figure 5<\/a>), the sample is vaporized and exposed to a high-energy electron beam that causes the sample\u2019s atoms (or molecules) to become electrically charged, typically by losing one or more electrons. These cations then pass through a (variable) electric or magnetic field that deflects each cation\u2019s path to an extent that depends on both its mass and charge (similar to how the path of a large steel ball bearing rolling past a magnet is deflected to a lesser extent that that of a small steel BB). The ions are detected, and a plot of the relative number of ions generated versus their mass-to-charge ratios (a <em>mass spectrum<\/em>) is made. The height of each vertical feature or peak in a mass spectrum is proportional to the fraction of cations with the specified mass-to-charge ratio. Since its initial use during the development of modern atomic theory, MS has evolved to become a powerful tool for chemical analysis in a wide range of applications.<\/p>\r\n\r\n<figure id=\"CNX_Chem_02_03_MassSpec\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"1300\"]<a href=\"https:\/\/opentextbc.ca\/chemistry\/wp-content\/uploads\/sites\/150\/2016\/05\/CNX_Chem_02_03_MassSpec.jpg\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CNX_Chem_02_03_MassSpec-2.jpg\" alt=\"The left diagram shows how a mass spectrometer works, which is primarily a large tube that bends downward at its midpoint. The sample enters on the left side of the tube. A heater heats the sample, causing it to vaporize. The sample is also hit with a beam of electrons as it is being vaporized. Charged particles from the sample, called ions, are then accelerated and pass between two magnets. The magnetic field deflects the lightest ions most. The deflection of the ions is measured by a detector located on the right side of the tube. The graph to the right of the spectrometer shows a mass spectrum of zirconium. The relative abundance, as a percentage from 0 to 100, is graphed on the y axis, and the mass to charge ratio is graphed on the x axis. The sample contains five different isomers of zirconium. Z R 90, which has a mass to charge ratio of 90, is the most abundant isotope at about 51 percent relative abundance. Z R 91 has a mass to charge ratio of 91 and a relative abundance of about 11 percent. Z R 92 has a mass to charge ratio of 92 and a relative abundance of about 18 percent. Z R 94 has a mass to charge ratio of 94 and a relative abundance of about 18 percent. Z R 96, which has a mass to charge ratio of 96, is the least abundant zirconium isotope with a relative abundance of about 2 percent.\" width=\"1300\" height=\"606\" \/><\/a> <strong>Figure 5.<\/strong> Analysis of zirconium in a mass spectrometer produces a mass spectrum with peaks showing the different isotopes of Zr.[\/caption]<\/figure>\r\n<div id=\"fs-idm122264832\" class=\"textbox shaded\">\r\n\r\n<span id=\"fs-idm93902544\"> <img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/OSC_Interactive_200-1-2.png\" alt=\"\u00a0\" width=\"91\" height=\"56\" class=\"alignleft\" \/><\/span>\r\n<p id=\"fs-idm136290400\">See an <a href=\"http:\/\/openstaxcollege.org\/l\/16MassSpec\">animation<\/a> that explains mass spectrometry. Watch this <a href=\"http:\/\/openstaxcollege.org\/l\/16RSChemistry\">video<\/a> from the Royal Society for Chemistry for a brief description of the rudiments of mass spectrometry.<\/p>\r\n\r\n<\/div>\r\n<\/section><section id=\"fs-idm131201632\" class=\"summary\">\r\n<h2>Key Concepts and Summary<\/h2>\r\n<p id=\"fs-idm148166800\">An atom consists of a small, positively charged nucleus surrounded by electrons. The nucleus contains protons and neutrons; its diameter is about 100,000 times smaller than that of the atom. The mass of one atom is usually expressed in atomic mass units (amu), which is referred to as the atomic mass. An amu is defined as exactly $latex \\frac{1}{12}$ of the mass of a carbon-12 atom and is equal to 1.6605 \u00d7 10<sup>\u221224<\/sup> g.<\/p>\r\n<p id=\"fs-idp228494288\">Protons are relatively heavy particles with a charge of 1+ and a mass of 1.0073 amu. Neutrons are relatively heavy particles with no charge and a mass of 1.0087 amu. Electrons are light particles with a charge of 1\u2212 and a mass of 0.00055 amu. The number of protons in the nucleus is called the atomic number (Z) and is the property that defines an atom\u2019s elemental identity. The sum of the numbers of protons and neutrons in the nucleus is called the mass number and, expressed in amu, is approximately equal to the mass of the atom. An atom is neutral when it contains equal numbers of electrons and protons.<\/p>\r\n<p id=\"fs-idm194069072\">Isotopes of an element are atoms with the same atomic number but different mass numbers; isotopes of an element, therefore, differ from each other only in the number of neutrons within the nucleus. When a naturally occurring element is composed of several isotopes, the atomic mass of the element represents the average of the masses of the isotopes involved. A chemical symbol identifies the atoms in a substance using symbols, which are one-, two-, or three-letter abbreviations for the atoms.<\/p>\r\n\r\n<\/section><section id=\"fs-idm7298256\" class=\"key-equations\">\r\n<h2>Key Equations<\/h2>\r\n<ul id=\"fs-idm175910672\">\r\n \t<li>$latex \\displaystyle{} \\text{average mass} = \\sum_{i} (\\text{fractional abundance} \\times \\text{isotopic mass})_i$<\/li>\r\n<\/ul>\r\n<div class=\"textbox exercises\">\r\n<h3 itemprop=\"educationalUse\">Exercises<\/h3>\r\n<p class=\"hanging-indent indent\">1. Write the symbol for each of the following ions:<\/p>\r\n<p id=\"fs-idp77154592\" class=\"hanging-indent indent\">a) the ion with a 1+ charge, atomic number 55, and mass number 133<\/p>\r\n<p id=\"fs-idm125607744\" class=\"hanging-indent indent\">b) the ion with 54 electrons, 53 protons, and 74 neutrons<\/p>\r\n<p id=\"fs-idm91510448\" class=\"hanging-indent indent\">c) the ion with atomic number 15, mass number 31, and a 3\u2212 charge<\/p>\r\n<p id=\"fs-idm78032064\" class=\"hanging-indent indent\">d) the ion with 24 electrons, 30 neutrons, and a 3+ charge<\/p>\r\n<p class=\"hanging-indent indent\">2. Open the <a href=\"http:\/\/openstaxcollege.org\/l\/16PhetAtomBld\">Build an Atom simulation<\/a> and click on the Atom icon.<\/p>\r\n<p id=\"fs-idm134679936\" class=\"hanging-indent indent\">a) Pick any one of the first 10 elements that you would like to build and state its symbol.<\/p>\r\n<p id=\"fs-idm125643536\" class=\"hanging-indent indent\">b) Drag protons, neutrons, and electrons onto the atom template to make an atom of your element.<\/p>\r\n<p class=\"hanging-indent indent\">State the numbers of protons, neutrons, and electrons in your atom, as well as the net charge and mass number.<\/p>\r\n<p id=\"fs-idm8547328\" class=\"hanging-indent indent\">c) Click on \u201cNet Charge\u201d and \u201cMass Number,\u201d check your answers to (b), and correct, if needed.<\/p>\r\n<p id=\"fs-idp210506208\" class=\"hanging-indent indent\">d) Predict whether your atom will be stable or unstable. State your reasoning.<\/p>\r\n<p id=\"fs-idp22922768\" class=\"hanging-indent indent\">e) Check the \u201cStable\/Unstable\u201d box. Was your answer to (d) correct? If not, first predict what you can do to make a stable atom of your element, and then do it and see if it works. Explain your reasoning.<\/p>\r\n<p class=\"hanging-indent indent\">3. Open the <a href=\"http:\/\/openstaxcollege.org\/l\/16PhetAtomBld\">Build an Atom simulation<\/a><\/p>\r\n<p id=\"fs-idm56609680\" class=\"hanging-indent indent\">a) Drag protons, neutrons, and electrons onto the atom template to make a neutral atom of Lithium-6 and give the isotope symbol for this atom.<\/p>\r\n<p id=\"fs-idm31990784\" class=\"hanging-indent indent\">b) Now remove one electron to make an ion and give the symbol for the ion you have created.<\/p>\r\n<p class=\"hanging-indent indent\">4. The following are properties of isotopes of two elements that are essential in our diet. Determine the number of protons, neutrons and electrons in each and name them.<\/p>\r\n<p id=\"fs-idp210102512\" class=\"hanging-indent indent\">a) atomic number 26, mass number 58, charge of 2+<\/p>\r\n<p id=\"fs-idp23141296\" class=\"hanging-indent indent\">b) atomic number 53, mass number 127, charge of 1\u2212<\/p>\r\n<p class=\"hanging-indent indent\">5. Give the number of protons, electrons, and neutrons in neutral atoms of each of the following isotopes:<\/p>\r\n<p id=\"fs-idm84436384\" class=\"hanging-indent indent\">a) $latex _3^7\\text{Li}$<\/p>\r\n<p id=\"fs-idm141443632\" class=\"hanging-indent indent\">b) $latex _{52}^{125}\\text{Te}$<\/p>\r\n<p id=\"fs-idm195681872\" class=\"hanging-indent indent\">c) $latex _{47}^{109}\\text{Ag}$<\/p>\r\n<p id=\"fs-idm82481216\" class=\"hanging-indent indent\">d) $latex _{7}^{15}\\text{N}$<\/p>\r\n<p id=\"fs-idm159280288\" class=\"hanging-indent indent\">e) $latex _{15}^{31}\\text{P}$<\/p>\r\n<p class=\"hanging-indent indent\">6. Average atomic masses listed by IUPAC are based on a study of experimental results. Bromine has two isotopes <sup>79<\/sup>Br and <sup>81<\/sup>Br, whose masses (78.9183 and 80.9163 amu) and abundances (50.69% and 49.31%) were determined in earlier experiments. Calculate the average atomic mass of bromine based on these experiments.<\/p>\r\n<p class=\"hanging-indent indent\">7. The average atomic masses of some elements may vary, depending upon the sources of their ores. Naturally occurring boron consists of two isotopes with accurately known masses (<sup>10<\/sup>B, 10.0129 amu and <sup>11<\/sup>B, 11.0931 amu). The average atomic mass of boron can vary from 10.807 to 10.819, depending on whether the mineral source is from Turkey or the United States. Calculate the percent abundances leading to the two values of the average atomic masses of boron from these two countries.<\/p>\r\n<p class=\"hanging-indent indent\">8. Explain Dalton's atomic theory.<\/p>\r\n<p class=\"hanging-indent indent\">9. Which is larger, a proton or an electron?<\/p>\r\n<p class=\"hanging-indent indent\">10. Which is larger, a neutron or an electron?<\/p>\r\n<p class=\"hanging-indent indent\">11. What are the charges for each of the three subatomic particles?<\/p>\r\n<p class=\"hanging-indent indent\">12. Where is most of the mass of an atom located?<\/p>\r\n<p class=\"hanging-indent indent\">13. Sketch a diagram of a boron atom, which has five protons and six neutrons in its nucleus.<\/p>\r\n<p class=\"hanging-indent indent\">14. Define <em class=\"emphasis\">atomic number<\/em>. What is the atomic number for a boron atom?<\/p>\r\n<p class=\"hanging-indent indent\">15. Define <em class=\"emphasis\">isotope<\/em> and give an example.<\/p>\r\n<p class=\"hanging-indent indent\">16. What is the difference between deuterium and tritium?<\/p>\r\n<p class=\"hanging-indent indent\">17. Which pair represents isotopes?<\/p>\r\n<p class=\"indent hanging-indent\">a) \u00a0<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2015\/11\/13_a_question.png\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/13_a_question.png\" alt=\"13_a_question\" width=\"103\" height=\"37\" class=\"alignnone wp-image-4880\" \/><\/a><span class=\"inlineequation\">\u00a0 \u00a0 \u00a0 b)<sub> \u00a026<\/sub>F and <sub>25<\/sub>M \u00a0 \u00a0 \u00a0 \u00a0<\/span><span class=\"inlineequation\">c)<sub> \u00a014<\/sub>S and <sub>15<\/sub>P<\/span><\/p>\r\n<p class=\"indent hanging-indent\">18. \u00a0Which pair represents isotopes?<span class=\"inlineequation\">a) \u00a0<sub>20<\/sub>C<\/span>\u00a0and <sub>19<\/sub>K \u00a0 \u00a0 \u00a0<span class=\"inlineequation\">b)<sub> \u00a026<\/sub>F\u00a0and\u00a0<sub>27<\/sub>F \u00a0 \u00a0 \u00a0 \u00a0<\/span><span class=\"inlineequation\">c)<sub> \u00a092<\/sub>U<\/span>\u00a0and\u00a0<span class=\"inlineequation\"><sub>92<\/sub>U\u00a0 \u00a0 \u00a0d)\u00a0$latex _7^{14}\\text{N}$\u00a0and\u00a0$latex _8^{14}\\text{N}$\u00a0<\/span><\/p>\r\n<p class=\"indent hanging-indent\">19. \u00a0Give complete symbols of each atom, including the atomic number and the mass number.<\/p>\r\n<p class=\"indent hanging-indent\">a) \u00a0an oxygen atom with 8 protons and 8 neutrons<\/p>\r\n<p class=\"indent hanging-indent\">b) \u00a0a potassium atom with 19 protons and 20 neutrons<\/p>\r\n<p class=\"indent hanging-indent\">c) \u00a0a lithium atom with 3 protons and 4 neutrons<\/p>\r\n<p class=\"indent hanging-indent\"><span style=\"font-size: 1em\">20. \u00a0Give complete symbols of each atom, including the atomic number and the mass number.<\/span><\/p>\r\na) \u00a0a magnesium atom with 12 protons and 12 neutrons\r\n\r\nb) \u00a0a magnesium atom with 12 protons and 13 neutrons\r\n\r\nc) \u00a0a xenon atom with 54 protons and 77 neutrons\r\n\r\n<span style=\"font-size: 1em\">21. \u00a0\u00a0 Americium-241 is an isotope used in smoke detectors. What is the complete symbol for this isotope?<\/span>\r\n\r\n<span style=\"font-size: 1em;text-indent: 2em\">22. \u00a0Carbon-14 is an isotope used to perform radioactive dating tests on previously living material. What is the complete symbol for this isotope?<\/span>\r\n\r\n<span style=\"font-size: 1em;text-indent: 2em\">23. \u00a0Give atomic symbols for each element.<\/span>\r\n\r\na) \u00a0sodium \u00a0 \u00a0\u00a0b) \u00a0argon \u00a0 \u00a0\u00a0c) \u00a0nitrogen \u00a0 \u00a0\u00a0d) \u00a0radon\r\n\r\n<span style=\"font-size: 1em;text-indent: 2em\">24. \u00a0Give atomic symbols for each element.<\/span>\r\n\r\na) \u00a0silver \u00a0 \u00a0\u00a0b) \u00a0gold \u00a0 \u00a0 \u00a0c) \u00a0mercury \u00a0 \u00a0 \u00a0d) \u00a0iodine\r\n\r\n<span style=\"font-size: 1em;text-indent: 2em\">25. \u00a0Give the name of the element.<\/span>\r\n\r\na) \u00a0Si \u00a0 \u00a0 \u00a0b) \u00a0Mn \u00a0 \u00a0 \u00a0c) \u00a0Fe \u00a0 \u00a0 \u00a0d) \u00a0Cr\r\n\r\n<span style=\"font-size: 1em;text-indent: 2em\">26. \u00a0Give the name of the element.<\/span>\r\n\r\na) \u00a0F \u00a0 \u00a0 \u00a0b) \u00a0Cl \u00a0 \u00a0 \u00a0c) \u00a0Br \u00a0 \u00a0 \u00a0d) \u00a0I\r\n\r\n27.\u00a0Determine the atomic mass of each element, given the isotopic composition.\r\n\r\na) \u00a0lithium, which is 92.4% lithium-7 (mass 7.016 u) and 7.60% lithium-6 (mass 6.015 u)\r\n\r\nb) \u00a0oxygen, which is 99.76% oxygen-16 (mass 15.995 u), 0.038% oxygen-17 (mass 16.999 u), and 0.205% oxygen-18 (mass 17.999 u)\r\n\r\n&nbsp;\r\n\r\n<strong>Answers<\/strong>\r\n<p id=\"fs-idm90412768\">1. (a) <sup>133<\/sup>Cs<sup>+<\/sup>; (b) <sup>127<\/sup>I<sup>\u2212<\/sup>; (c) <sup>31<\/sup>P<sup>3\u2212<\/sup>; (d) <sup>57<\/sup>Co<sup>3+<\/sup><\/p>\r\n<p id=\"fs-idm124722320\">2. (a) Carbon-12, <sup>12<\/sup>C; (b) This atom contains six protons and six neutrons. There are six electrons in a neutral <sup>12<\/sup>C atom. The net charge of such a neutral atom is zero, and the mass number is 12. (c) The preceding answers are correct. (d) The atom will be stable since C-12 is a stable isotope of carbon. (e) The preceding answer is correct. Other answers for this exercise are possible if a different element of isotope is chosen.<\/p>\r\n<p id=\"fs-idm134038192\">3. (a) Lithium-6 contains three protons, three neutrons, and three electrons. The isotope symbol is <sup>6<\/sup>Li or $latex _3^6\\text{Li}$. (b) <sup>6<\/sup>Li<sup>+<\/sup> or $latex _3^6 \\text{Li}^+$<\/p>\r\n<p id=\"fs-idm58517792\">4. (a) Iron, 26 protons, 24 electrons, and 32 neutrons; (b) iodine, 53 protons, 54 electrons, and 74 neutrons<\/p>\r\n<p id=\"fs-idm60087264\">5. (a) 3 protons, 3 electrons, 4 neutrons; (b) 52 protons, 52 electrons, 73 neutrons; (c) 47 protons, 47 electrons, 62 neutrons; (d) 7 protons, 7 electrons, 8 neutrons; (e) 15 protons, 15 electrons, 16 neutrons<\/p>\r\n<p id=\"fs-idm9833872\">6. 79.904 amu<\/p>\r\n<p id=\"fs-idm4806656\">7. Turkey source: 0.2649 (of 10.0129 amu isotope); US source: 0.2537 (of 10.0129 amu isotope)<\/p>\r\n8. All matter is composed of atoms; atoms of the same element are the same, and atoms of different elements are different; atoms combine in whole-number ratios to form compounds.\r\n\r\n9.\u00a0A proton is larger than an electron.\r\n10. A neutron is larger than an electron.\r\n11. proton: 1+; electron: 1\u2212; neutron: 0\r\n12. \u00a0Most of the mass of an atom is located in the nucleus.\r\n\r\n<span style=\"font-size: 1em\">13.<\/span><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/Nucleus.png\" style=\"font-size: 1em\"><img src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/Nucleus-1.png\" alt=\"Nucleus\" width=\"160\" height=\"160\" class=\"alignnone wp-image-4630\" \/><\/a>\r\n\r\n<span style=\"font-size: 1em\">14.\u00a0The atomic number is the number of protons in a nucleus. Boron has an atomic number of five.<\/span>\r\n\r\n<span style=\"font-size: 1em\">15.\u00a0Isotopes are atoms of the same element but with different numbers of neutrons.<\/span>\r\n\r\n<span style=\"font-size: 1em\">16. They are isotopes, therefore the difference between deuterium and tritium is the number of neutrons. \u00a0Deuterium has one, and tritium has two.<\/span>\r\n\r\n<span style=\"font-size: 1em\">17. (a)<\/span>\r\n\r\n<span style=\"font-size: 1em\">18.\u00a0 (b) - note: there is an error with option (d) for the atomic number of nitrogen can only be 7.<\/span>\r\n\r\n<span style=\"font-size: 1em\">19. \u00a0<\/span><span style=\"font-size: 1em\">a) $latex _{8}^{16}\\text{O}$ \u00a0 \u00a0 \u00a0<\/span><span style=\"font-size: 1em\">b) \u00a0$latex _{19}^{39}\\text{K}$ \u00a0 \u00a0 \u00a0c) \u00a0$latex _{3}^{7}\\text{Li}$<\/span>\r\n\r\n<span style=\"font-size: 1em\">20. \u00a0Give complete symbols of each atom, including the atomic number and the mass number.<\/span>\r\n<div class=\"question\">\r\n\r\na) \u00a0$latex _{12}^{24}\\text{Mg}$ \u00a0 \u00a0 \u00a0b) \u00a0$latex _{12}^{25}\\text{Mg}$ \u00a0 \u00a0 \u00a0c) \u00a0$latex _{54}^{131}\\text{Xe}$\r\n\r\n<\/div>\r\n<div class=\"question\">\r\n<p id=\"ball-ch03_s01_qs01_p27\" class=\"para\">21. \u00a0\u00a0$latex _{95}^{241}\\text{Am}$<\/p>\r\n\r\n<\/div>\r\n<span style=\"font-size: 1em\">22. \u00a0$latex _{6}^{14}\\text{C}$<\/span>\r\n\r\n<span style=\"font-size: 1em\">23. \u00a0<\/span><span style=\"font-size: 1em\">a) \u00a0Na \u00a0 \u00a0 b) \u00a0Ar \u00a0 \u00a0 c) \u00a0N \u00a0 \u00a0\u00a0d) \u00a0Rn<\/span>\r\n\r\n<span style=\"font-size: 1em\">24. \u00a0a<\/span><span style=\"font-size: 1em\">) \u00a0Ag \u00a0 \u00a0 b) \u00a0Au \u00a0 \u00a0 \u00a0c) \u00a0Hg \u00a0 \u00a0 \u00a0d) \u00a0I<\/span>\r\n\r\n<span style=\"font-size: 1em\">25. \u00a0a<\/span><span style=\"font-size: 1em\">) \u00a0silicon \u00a0 \u00a0 \u00a0b) \u00a0manganese \u00a0 \u00a0 \u00a0c) \u00a0iron \u00a0 \u00a0 \u00a0d) \u00a0chromium<\/span>\r\n\r\n<span style=\"font-size: 1em\">26. \u00a0a<\/span><span style=\"font-size: 1em\">) \u00a0fluorine \u00a0 \u00a0 \u00a0b) \u00a0chlorine \u00a0 \u00a0 \u00a0c) \u00a0bromine \u00a0 \u00a0 \u00a0d) \u00a0iodine<\/span>\r\n\r\n27. \u00a0a) \u00a06.940 u \u00a0 \u00a0\u00a0b) \u00a016.000 u\r\n\r\n<\/div>\r\n<h2>Glossary<\/h2>\r\n<strong>electron:\u00a0<\/strong>negatively charged, subatomic particle of relatively low mass located outside the nucleus\r\n\r\n<strong>anion:\u00a0<\/strong>negatively charged atom or molecule (contains more electrons than protons)\r\n\r\n<strong>atomic mass:\u00a0<\/strong>average mass of atoms of an element, expressed in amu\r\n\r\n<strong>atomic mass unit (amu):\u00a0<\/strong>(also, unified atomic mass unit, u, or Dalton, Da) unit of mass equal to $latex \\frac{1}{12}$ of the mass of a <sup>12<\/sup>C atom\r\n\r\n<strong>atomic number (Z):\u00a0<\/strong>number of protons in the nucleus of an atom\r\n\r\n<strong>cation:\u00a0<\/strong>positively charged atom or molecule (contains fewer electrons than protons)\r\n\r\n<strong>chemical symbol:\u00a0<\/strong>one-, two-, or three-letter abbreviation used to represent an element or its atoms\r\n\r\n<strong>Dalton (Da):\u00a0<\/strong>alternative unit equivalent to the atomic mass unit\r\n\r\n<strong>fundamental unit of charge:\u00a0<\/strong>(also called the elementary charge) equals the magnitude of the charge of an electron (e) with e = 1.602 \u00d7 10<sup>\u221219<\/sup> C\r\n\r\n<strong>ion:\u00a0<\/strong>electrically charged atom or molecule (contains unequal numbers of protons and electrons)\r\n\r\n<strong>isotopic mass:\u00a0<\/strong>mass of an isotope of an element, expressed in amu\r\n\r\n<strong>mass number (A):\u00a0<\/strong>sum of the numbers of neutrons and protons in the nucleus of an atom\r\n\r\n<strong>unified atomic mass unit (u):\u00a0<\/strong>alternative unit equivalent to the atomic mass unit\r\n\r\n<\/section>","rendered":"<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>Write and interpret symbols that depict the atomic number, mass number, and charge of an atom or ion<\/li>\n<li>Define the atomic mass unit and average atomic mass<\/li>\n<li>Calculate average atomic mass and isotopic abundance<\/li>\n<\/ul>\n<\/div>\n<p id=\"fs-idp188136384\">The development of modern atomic theory revealed much about the inner structure of atoms. It was learned that an atom contains a very small nucleus composed of positively charged protons and uncharged neutrons, surrounded by a much larger volume of space containing negatively charged electrons. The nucleus contains the majority of an atom\u2019s mass because protons and neutrons are much heavier than electrons, whereas electrons occupy almost all of an atom\u2019s volume. The diameter of an atom is on the order of 10<sup>\u221210<\/sup> m, whereas the diameter of the nucleus is roughly 10<sup>\u221215<\/sup> m\u2014about 100,000 times smaller. For a perspective about their relative sizes, consider this: If the nucleus were the size of a blueberry, the atom would be about the size of a football stadium (<a href=\"#CNX_Chem_02_03_AtomSize\" class=\"autogenerated-content\">Figure 1<\/a>).<\/p>\n<figure id=\"CNX_Chem_02_03_AtomSize\"><figcaption>\n<figure style=\"width: 1300px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/opentextbc.ca\/chemistry\/wp-content\/uploads\/sites\/150\/2016\/05\/CNX_Chem_02_03_AtomSize.jpg\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CNX_Chem_02_03_AtomSize-2.jpg\" alt=\"The diagram on the left shows a picture of an atom that is 10 to the negative tenth power meters in diameter. The nucleus is labeled at the center of the atom and is 10 to the negative fifteenth power meters. The central figure shows a photograph of an American football stadium. The figure on the right shows a photograph of a person with a handful of blueberries.\" width=\"1300\" height=\"400\" \/><\/a><figcaption class=\"wp-caption-text\"><strong>Figure 1.<\/strong> If an atom could be expanded to the size of a football stadium, the nucleus would be the size of a single blueberry. (credit middle: modification of work by \u201cbabyknight\u201d\/Wikimedia Commons; credit right: modification of work by Paxson Woelber)<\/figcaption><\/figure>\n<\/figcaption><\/figure>\n<p id=\"fs-idm171776576\">Atoms\u2014and the protons, neutrons, and electrons that compose them\u2014are extremely small. For example, a carbon atom weighs less than 2 \u00d7 10<sup>\u221223<\/sup> g, and an electron has a charge of less than 2 \u00d7 10<sup>\u221219<\/sup> C (coulomb). When describing the properties of tiny objects such as atoms, we use appropriately small units of measure, such as the <strong>atomic mass unit (amu)<\/strong> and the <strong>fundamental unit of charge (e)<\/strong>. The amu was originally defined based on hydrogen, the lightest element, then later in terms of oxygen. Since 1961, it has been defined with regard to the most abundant isotope of carbon, atoms of which are assigned masses of exactly 12 amu. (This isotope is known as \u201ccarbon-12\u201d as will be discussed later in this module.) Thus, one amu is exactly [latex]\\frac{1}{12}[\/latex] of the mass of one carbon-12 atom: 1 amu = 1.6605 \u00d7 10<sup>\u221224<\/sup> g. (The <strong>Dalton (Da)<\/strong> and the <strong>unified atomic mass unit (u)<\/strong> are alternative units that are equivalent to the amu.) The fundamental unit of charge (also called the elementary charge) equals the magnitude of the charge of an electron (e) with e = 1.602 \u00d7 10<sup>\u221219<\/sup> C.<\/p>\n<p id=\"fs-idm166273840\">A proton has a mass of 1.0073 amu and a charge of 1+. A neutron is a slightly heavier particle with a mass 1.0087 amu and a charge of zero; as its name suggests, it is neutral. The electron has a charge of 1\u2212 and is a much lighter particle with a mass of about 0.00055 amu (it would take about 1800 electrons to equal the mass of one proton. The properties of these fundamental particles are summarized in <a href=\"#fs-idp90857696\" class=\"autogenerated-content\">Table 1<\/a>. (An observant student might notice that the sum of an atom\u2019s subatomic particles does not equal the atom\u2019s actual mass: The total mass of six protons, six neutrons, and six electrons is 12.0993 amu, slightly larger than 12.00 amu. This \u201cmissing\u201d mass is known as the mass defect, and you will learn about it in the chapter on nuclear chemistry.)<\/p>\n<p id=\"fs-idp27048016\">The number of protons in the nucleus of an atom is its <strong>atomic number (Z)<\/strong>. This is the defining trait of an element: Its value determines the identity of the atom. For example, any atom that contains six protons is the element carbon and has the atomic number 6, regardless of how many neutrons or electrons it may have. A neutral atom must contain the same number of positive and negative charges, so the number of protons equals the number of electrons. Therefore, the atomic number also indicates the number of electrons in an atom. The total number of protons and neutrons in an atom is called its <strong>mass number (A)<\/strong>. The number of neutrons is therefore the difference between the mass number and the atomic number: A \u2013 Z = number of neutrons.<\/p>\n<p style=\"text-align: center\">[latex]\\begin{array}{r @ {{}={}} l} \\text{atomic number (Z)} & \\text{number of protons} \\\\[1em] \\text{mass number (A)} & \\text{number of protons + number of neutrons} \\\\[1em] \\text{A - Z} & \\text{number of neutrons} \\end{array}[\/latex]<\/p>\n<table id=\"fs-idp90857696\" class=\"span-all\" summary=\"This table gives the name, location, charge in C, unit charge, mass in A M U and mass in grams for electrons, protons and neutrons. Electrons are located outside of the nucleus, have a charge of negative 1.602 times 10 to the negative nineteenth power, a unit charge of negative 1, and a mass of 0.00055 A M U or 0.00091 times 10 to the negative twenty-fourth power grams. Protons are located within the nucleus, have a charge of 1.602 times 10 to the negative nineteenth power, have a unit charge of positive 1, and have a mass of 1.0073 A M U or 1.6726 times 10 to the negative twenty-fourth power grams. Neutrons are located within the nucleus, have a charge of 0, have a unit charge of 0, and have a mass of 1.0087 A M U or 1.6749 times 10 to the negative twenty-fourth power grams.\">\n<thead>\n<tr valign=\"top\">\n<th>Name<\/th>\n<th>Location<\/th>\n<th>Charge (C)<\/th>\n<th>Unit Charge<\/th>\n<th>Mass (amu)<\/th>\n<th>Mass (g)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr valign=\"top\">\n<td>electron<\/td>\n<td>outside nucleus<\/td>\n<td>\u22121.602 \u00d7 10<sup>\u221219<\/sup><\/td>\n<td>1\u2212<\/td>\n<td>0.00055<\/td>\n<td>0.00091 \u00d7 10<sup>\u221224<\/sup><\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>proton<\/td>\n<td>nucleus<\/td>\n<td>1.602 \u00d7 10<sup>\u221219<\/sup><\/td>\n<td>1+<\/td>\n<td>1.00727<\/td>\n<td>1.67262 \u00d7 10<sup>\u221224<\/sup><\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>neutron<\/td>\n<td>nucleus<\/td>\n<td>0<\/td>\n<td>0<\/td>\n<td>1.00866<\/td>\n<td>1.67493 \u00d7 10<sup>\u221224<\/sup><\/td>\n<\/tr>\n<tr>\n<td colspan=\"6\"><strong>Table 1.<\/strong> Properties of Subatomic Particles<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p id=\"fs-idm159569776\">Atoms are electrically neutral if they contain the same number of positively charged protons and negatively charged electrons. When the numbers of these subatomic particles are <em>not<\/em> equal, the atom is electrically charged and is called an <strong>ion<\/strong>. The charge of an atom is defined as follows:<\/p>\n<p id=\"fs-idp142952368\">Atomic charge = number of protons \u2212 number of electrons<\/p>\n<p id=\"fs-idp59351760\">As will be discussed in more detail later in this chapter, atoms (and molecules) typically acquire charge by gaining or losing electrons. An atom that gains one or more electrons will exhibit a negative charge and is called an <strong>anion<\/strong>. Positively charged atoms called <strong>cations<\/strong> are formed when an atom loses one or more electrons. For example, a neutral sodium atom (Z = 11) has 11 electrons. If this atom loses one electron, it will become a cation with a 1+ charge (11 \u2212 10 = 1+). A neutral oxygen atom (Z = 8) has eight electrons, and if it gains two electrons it will become an anion with a 2\u2212 charge (8 \u2212 10 = 2\u2212).<\/p>\n<div class=\"textbox shaded\" id=\"fs-idm5511728\">\n<h3>Example 1<\/h3>\n<p id=\"fs-idm54131248\">Iodine is an essential trace element in our diet; it is needed to produce thyroid hormone. Insufficient iodine in the diet can lead to the development of a goiter, an enlargement of the thyroid gland (<a href=\"#CNX_Chem_02_03_Iodine\" class=\"autogenerated-content\">Figure 2<\/a>).<\/p>\n<figure id=\"CNX_Chem_02_03_Iodine\"><figcaption>\n<figure style=\"width: 975px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/opentextbc.ca\/chemistry\/wp-content\/uploads\/sites\/150\/2016\/05\/CNX_Chem_02_03_Iodine.jpg\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CNX_Chem_02_03_Iodine-2.jpg\" alt=\"Figure A shows a photo of a person who has a very swollen thyroid in his or her neck. Figure B shows a photo of a canister of iodized salt.\" width=\"975\" height=\"432\" \/><\/a><figcaption class=\"wp-caption-text\"><strong>Figure 2.<\/strong> (a) Insufficient iodine in the diet can cause an enlargement of the thyroid gland called a goiter. (b) The addition of small amounts of iodine to salt, which prevents the formation of goiters, has helped eliminate this concern in the US where salt consumption is high. (credit a: modification of work by \u201cAlmazi\u201d\/Wikimedia Commons; credit b: modification of work by Mike Mozart)<\/figcaption><\/figure>\n<\/figcaption><\/figure>\n<p id=\"fs-idm90509824\">The addition of small amounts of iodine to table salt (iodized salt) has essentially eliminated this health concern in the United States, but as much as 40% of the world\u2019s population is still at risk of iodine deficiency. The iodine atoms are added as anions, and each has a 1\u2212 charge and a mass number of 127. Determine the numbers of protons, neutrons, and electrons in one of these iodine anions.<\/p>\n<p>&nbsp;<\/p>\n<p id=\"fs-idp104898720\"><strong>Solution<\/strong><\/p>\n<p>The atomic number of iodine (53) tells us that a neutral iodine atom contains 53 protons in its nucleus and 53 electrons outside its nucleus. Because the sum of the numbers of protons and neutrons equals the mass number, 127, the number of neutrons is 74 (127 \u2212 53 = 74). Since the iodine is added as a 1\u2212 anion, the number of electrons is 54 [53 \u2013 (1\u2013) = 54].<\/p>\n<p>&nbsp;<\/p>\n<p><em><strong>Test Yourself<\/strong><\/em><\/p>\n<p>An ion of platinum has a mass number of 195 and contains 74 electrons. How many protons and neutrons does it contain, and what is its charge?<\/p>\n<p>&nbsp;<\/p>\n<p><strong><em>Answers<\/em><\/strong><\/p>\n<p>78 protons; 117 neutrons; charge is 4+<\/p>\n<\/div>\n<section id=\"fs-idm176092496\">\n<div class=\"textbox shaded\">\n<h3 class=\"title\">Example 2<\/h3>\n<ol id=\"ball-ch03_s01_l03\" class=\"orderedlist\">\n<li>The most common carbon atoms have six protons and six neutrons in their nuclei. What are the atomic number and the mass number of these carbon atoms?<\/li>\n<li>An isotope of uranium has an atomic number of 92 and a mass number of 235. What are the number of protons and neutrons in the nucleus of this atom?<\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n<p class=\"simpara\"><strong>Solution<\/strong><\/p>\n<ol id=\"ball-ch03_s01_l04\" class=\"orderedlist\">\n<li>If a carbon atom has six protons in its nucleus, its atomic number is 6. If it also has six neutrons in the nucleus, then the mass number is 6 +\u00a06, or 12.<\/li>\n<li>If the atomic number of uranium is 92, then that is the number of protons in the nucleus. Because the mass number is 235, then the number of neutrons in the nucleus is 235 \u2212 92, or 143.<\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n<p class=\"simpara\"><strong><em class=\"emphasis bolditalic\">Test Yourself<\/em><\/strong><\/p>\n<p id=\"ball-ch03_s01_p09\" class=\"para\">The number of protons in the nucleus of a tin atom is 50, while the number of neutrons in the nucleus is 68. What are the atomic number and the mass number of this isotope?<\/p>\n<p>&nbsp;<\/p>\n<p class=\"simpara\"><strong><em class=\"emphasis\">Answer<\/em><\/strong><\/p>\n<p id=\"ball-ch03_s01_p10\" class=\"para\">Atomic number = 50, mass number = 118<\/p>\n<\/div>\n<h2>Chemical Symbols<\/h2>\n<p id=\"fs-idm48306304\">A <strong>chemical symbol<\/strong> is an abbreviation that we use to indicate an element or an atom of an element. For example, the symbol for mercury is Hg (<a href=\"#CNX_Chem_02_03_SiSymbol\" class=\"autogenerated-content\">Figure 3<\/a>). We use the same symbol to indicate one atom of mercury (microscopic domain) or to label a container of many atoms of the element mercury (macroscopic domain).<\/p>\n<figure id=\"CNX_Chem_02_03_SiSymbol\">\n<figure id=\"attachment_1312\" aria-describedby=\"caption-attachment-1312\" style=\"width: 200px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CNX_Chem_02_03_SiSymbol-2-e1528932573783.jpg\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CNX_Chem_02_03_SiSymbol-2-e1528932573783.jpg\" alt=\"\" width=\"200\" height=\"160\" class=\"wp-image-1312 size-full\" \/><\/a><figcaption id=\"caption-attachment-1312\" class=\"wp-caption-text\"><strong>Figure 3.<\/strong> The symbol Hg represents the element mercury regardless of the amount; it could represent one atom of mercury or a large amount of mercury.<\/figcaption><\/figure>\n<\/figure>\n<p>The symbols for several common elements and their atoms are listed in <a href=\"#fs-idm36686800\" class=\"autogenerated-content\">Table 2<\/a>. Some symbols are derived from the common name of the element; others are abbreviations of the name in another language. Most symbols have one or two letters, but three-letter symbols have been used to describe some elements that have atomic numbers greater than 112. To avoid confusion with other notations, only the first letter of a symbol is capitalized. For example, Co is the symbol for the element cobalt, but CO is the notation for the compound carbon monoxide, which contains atoms of the elements carbon (C) and oxygen (O). All known elements and their symbols are in the periodic table in <a href=\"https:\/\/opentextbc.ca\/chemistry\/chapter\/2-5-the-periodic-table\/#CNX_Chem_02_05_PerTable1\" class=\"autogenerated-content\" target=\"_blank\" rel=\"noopener\">Figure 2 in Chapter 3.5 The Periodic Table<\/a> (also found in <a href=\"https:\/\/opentextbc.ca\/chemistry\/back-matter\/the-periodic-table\/\" class=\"autogenerated-content\" target=\"_blank\" rel=\"noopener\">Appendix A<\/a>).<\/p>\n<table id=\"fs-idm36686800\" class=\"span-all\" summary=\"This table has two columns labeled element and symbol. The first letter of the symbol is always an uppercase letter while the second letter of the symbol is always a lowercase letter. Aluminum has the symbol A L. Bromine has the symbol B R, calcium has the symbol C A, carbon has the symbol C, chlorine has the symbol C L, chromium has the symbol C R, cobalt has the symbol C O, copper has the symbol C U, from cuprum, fluorine has the symbol F, gold has the symbol A U, from aurum, helium has the symbol H E, hydrogen has the symbol H, iodine has the symbol I, iron has the symbol F E, from ferrum, lead has the symbol P B, from plumbum, magnesium has the symbol M G, mercury has the symbol H G from hydrargyrum, nitrogen has the symbol N, oxygen has the symbol O, potassium has the symbol K, from kalium, silicon has the symbol S I, silver has the symbol A G, from argentum, sodium has the symbol N A from natrium, sulfur has the symbol S, tin has the symbol S N from stannum, and zinc has the symbol Z N.\">\n<thead>\n<tr valign=\"top\">\n<th>Element<\/th>\n<th>Symbol<\/th>\n<th>Element<\/th>\n<th>Symbol<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr valign=\"top\">\n<td>aluminum<\/td>\n<td>Al<\/td>\n<td>iron<\/td>\n<td>Fe (from <em>ferrum<\/em>)<\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>bromine<\/td>\n<td>Br<\/td>\n<td>lead<\/td>\n<td>Pb (from <em>plumbum<\/em>)<\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>calcium<\/td>\n<td>Ca<\/td>\n<td>magnesium<\/td>\n<td>Mg<\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>carbon<\/td>\n<td>C<\/td>\n<td>mercury<\/td>\n<td>Hg (from <em>hydrargyrum<\/em>)<\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>chlorine<\/td>\n<td>Cl<\/td>\n<td>nitrogen<\/td>\n<td>N<\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>chromium<\/td>\n<td>Cr<\/td>\n<td>oxygen<\/td>\n<td>O<\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>cobalt<\/td>\n<td>Co<\/td>\n<td>potassium<\/td>\n<td>K (from <em>kalium<\/em>)<\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>copper<\/td>\n<td>Cu (from <em>cuprum<\/em>)<\/td>\n<td>silicon<\/td>\n<td>Si<\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>fluorine<\/td>\n<td>F<\/td>\n<td>silver<\/td>\n<td>Ag (from<em> argentum<\/em>)<\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>gold<\/td>\n<td>Au (from <em>aurum<\/em>)<\/td>\n<td>sodium<\/td>\n<td>Na (from <em>natrium<\/em>)<\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>helium<\/td>\n<td>He<\/td>\n<td>sulfur<\/td>\n<td>S<\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>hydrogen<\/td>\n<td>H<\/td>\n<td>tin<\/td>\n<td>Sn (from <em>stannum<\/em>)<\/td>\n<\/tr>\n<tr valign=\"top\">\n<td>iodine<\/td>\n<td>I<\/td>\n<td>zinc<\/td>\n<td>Zn<\/td>\n<\/tr>\n<tr>\n<td colspan=\"4\"><strong>Table 2.<\/strong> Some Common Elements and Their Symbols<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p id=\"fs-idm105035264\">Traditionally, the discoverer (or discoverers) of a new element names the element. However, until the name is recognized by the International Union of Pure and Applied Chemistry (IUPAC), the recommended name of the new element is based on the Latin word(s) for its atomic number. For example, element 106 was called unnilhexium (Unh), element 107 was called unnilseptium (Uns), and element 108 was called unniloctium (Uno) for several years. These elements are now named after scientists (or occasionally locations); for example, element 106 is now known as <em>seaborgium<\/em> (Sg) in honor of Glenn Seaborg, a Nobel Prize winner who was active in the discovery of several heavy elements.<\/p>\n<div id=\"fs-idm111013376\" class=\"textbox shaded\">\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/OSC_Interactive_200-1-2.png\" alt=\"\u00a0\" width=\"119\" height=\"74\" class=\"alignleft\" \/><\/p>\n<p id=\"fs-idm3892928\">Visit this <a href=\"http:\/\/openstaxcollege.org\/l\/16IUPAC\">site<\/a> to learn more about IUPAC, the International Union of Pure and Applied Chemistry, and explore its periodic table.<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<\/section>\n<section id=\"fs-idp42149200\">\n<h2>Isotopes<\/h2>\n<p id=\"fs-idm240748912\">The symbol for a specific isotope of any element is written by placing the mass number as a superscript to the left of the element symbol (<a href=\"#CNX_Chem_02_03_AtomSym\" class=\"autogenerated-content\">Figure 4<\/a>). The atomic number is sometimes written as a subscript preceding the symbol, but since this number defines the element\u2019s identity, as does its symbol, it is often omitted. For example, magnesium exists as a mixture of three isotopes, each with an atomic number of 12 and with mass numbers of 24, 25, and 26, respectively. These isotopes can be identified as <sup>24<\/sup>Mg, <sup>25<\/sup>Mg, and <sup>26<\/sup>Mg. These isotope symbols are read as \u201celement, mass number\u201d and can be symbolized consistent with this reading. For instance, <sup>24<\/sup>Mg is read as \u201cmagnesium 24,\u201d and can be written as \u201cmagnesium-24\u201d or \u201cMg-24.\u201d <sup>25<\/sup>Mg is read as \u201cmagnesium 25,\u201d and can be written as \u201cmagnesium-25\u201d or \u201cMg-25.\u201d All magnesium atoms have 12 protons in their nucleus. They differ only because a <sup>24<\/sup>Mg atom has 12 neutrons in its nucleus, a <sup>25<\/sup>Mg atom has 13 neutrons, and a <sup>26<\/sup>Mg has 14 neutrons. \u00a0Therefore the masses of isotopes of an element, <strong>isotopic mass<\/strong>, differ &#8211; see Table 3.<\/p>\n<p>&nbsp;<\/p>\n<figure id=\"CNX_Chem_02_03_AtomSym\">\n<figure style=\"width: 492px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/opentextbc.ca\/chemistry\/wp-content\/uploads\/sites\/150\/2016\/05\/CNX_Chem_02_03_AtomSym.jpg\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CNX_Chem_02_03_AtomSym-2.jpg\" alt=\"This diagram shows the symbol for helium, \u201cH e.\u201d The number to the upper left of the symbol is the mass number, which is 4. The number to the upper right of the symbol is the charge which is positive 2. The number to the lower left of the symbol is the atomic number, which is 2. This number is often omitted. Also shown is \u201cM g\u201d which stands for magnesium It has a mass number of 24, a charge of positive 2, and an atomic number of 12.\" width=\"492\" height=\"109\" class=\"\" \/><\/a><figcaption class=\"wp-caption-text\"><strong>Figure 4.<\/strong> The symbol for an atom indicates the element via its usual two-letter symbol, the mass number as a left superscript, the atomic number as a left subscript (sometimes omitted), and the charge as a right superscript.<\/figcaption><\/figure>\n<\/figure>\n<p id=\"fs-idm198096624\">Information about the naturally occurring isotopes of elements with atomic numbers 1 through 10 is given in <a href=\"#fs-idm87646592\" class=\"autogenerated-content\">Table 3<\/a>. Note that in addition to standard names and symbols, the isotopes of hydrogen are often referred to using common names and accompanying symbols. Hydrogen-2, symbolized <sup>2<\/sup>H, is also called deuterium and sometimes symbolized D. Hydrogen-3, symbolized <sup>3<\/sup>H, is also called tritium and sometimes symbolized T.<\/p>\n<table id=\"fs-idm87646592\" class=\"span-all\" style=\"width: 513px;height: 1429px\" summary=\"This table has seven columns labeled element, symbol, atomic number, number of protons, number of neutrons, mass in A M U, and percent natural abundance. The symbols for each element each show the mass number in the upper left and the atomic number in the lower left. Therefore hydrogen left superscript 1, left subscript 1, or protium, has a mass number of 1 and an atomic number of 1. Protium has one proton, 0 neutrons, a mass of 1.0078 and a natural abundance percentage of 99.985. Hydrogen left superscript 2, left subscript 1, or deuterium, has an atomic number of 1, 1 proton, 1 neutron, a mass of 2.0141 and a natural abundance percentage of 0.015. Hydrogen left superscript 3, left subscript 1, or tritium, has an atomic number of 11 protons, 2 neutrons, and a mass of 3.01605. No natural abundance percentage is given. Helium left superscript 3, left subscript 2 has an atomic number of 2, 2 protons, 1 neutron, a mass of 3.01603, and a natural abundance percentage of 0.00013. Helium left superscript 4, left subscript 2 has an atomic number of 2, 2 protons, 2 neutrons, a mass of 4.0026 and a natural abundance percentage of 100. Lithium left superscript 6, left subscript 3 has an atomic number of 3, 3 protons, 3 neutrons, a mass of 6.0151, and a natural abundance percentage of 7.42. Lithium left superscript 7, left subscript 3 has an atomic number of 3, 3 protons, 4 neutrons, a mass of 7.0160, and a natural abundance percentage of 92.8. Beryllium left superscript 9, left subscript 4 has an atomic number of 4, 4 protons, 5 neutrons, a mass of 9.0122, and a natural abundance percentage of 100. Boron left superscript 10, left subscript 5 has an atomic number of 5, 5 protons, 5 neutrons and a natural abundance percentage of 19.9. Boron left superscript 11, left subscript 5 has an atomic number of 5, 5 protons, 6 neutrons, a mass of 11.0093 and a natural abundance of 80.1. Carbon left superscript 12, left subscript 6 has an atomic number of 6, 6 protons, 6 neutrons, a mass of 12, and a natural abundance percentage of 98.89. Carbon left superscript 13, left subscript 6 has an atomic number of 6, 6 protons, 7 neutrons, a mass of 13.0033, and a natural abundance percentage of 1.11. Carbon left superscript 14, left subscript 6 has an atomic number of 6, 6 protons, 8 neutrons, and a mass of 14.0032. Its natural abundance percentage is not reported. Nitrogen left superscript 14, left subscript 7 has an atomic number of 7, 7 protons, 7 neutrons, a mass of 14.0031, and a natural abundance percentage of 99.63. Nitrogen left superscript 15, left subscript 7 has an atomic number of 7, 7 protons, 8 neutrons, a mass of 15.0001, and a natural abundance percentage of 0.37. Oxygen left superscript 16, left subscript 8 has an atomic number of 8, 8 protons, 8 neutrons, a mass of 15.9949, and a natural abundance percentage of 99.759. Oxygen left superscript 17, left subscript 8 has an atomic number of 8, 8 protons, 9 neutrons, a mass of 16.9991, and a natural abundance percentage of 0.037. Oxygen left superscript 18, left subscript 8 has an atomic number of 8, 8 protons, 10 neutrons, a mass of 17.9992, and a natural abundance percentage of 0.204. Fluorine left superscript 19, left subscript 9 has an atomic number of 9, 9 protons, 10 neutrons, a mass of 18.9984, and a natural abundance percentage of 100. Neon left superscript 20, left subscript 10 has an atomic number of 10, 10 protons, 10 neutrons, a mass of 19.9924, and a natural abundance percentage of 90.92. Neon left superscript 21, left subscript 10 has an atomic number of 10, 10 protons, 11 neutrons, a mass of 20.994, and a natural abundance percentage of 0.257. Neon left superscript 22, left subscript 10 has an atomic number of 10, 10 protons, 12 neutrons, a mass of 21.9914, and a natural abundance percentage of 8.82.\">\n<thead>\n<tr style=\"height: 72px\" valign=\"top\">\n<th style=\"width: 62.21875px;height: 72px\">Element<\/th>\n<th style=\"width: 148.6875px;height: 72px\">Symbol<\/th>\n<th style=\"width: 46.21875px;height: 72px\"><sup>Atomic Number<\/sup><\/th>\n<th style=\"width: 43.109375px;height: 72px\"><sup># of Protons<\/sup><\/th>\n<th style=\"width: 51.046875px;height: 72px\"><sup># of Neutrons<\/sup><\/th>\n<th style=\"width: 54.234375px;height: 72px\">Isotopic Mass (amu)<\/th>\n<th style=\"width: 78.25px;height: 72px;text-align: left\">% Natural Abundance<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr style=\"height: 136px\" valign=\"middle\">\n<td style=\"width: 62.21875px;text-align: center;height: 408px\" rowspan=\"3\">hydrogen<\/td>\n<td style=\"width: 148.6875px;text-align: center;height: 136px\">[latex]_1^1\\text{H}[\/latex]<\/p>\n<div><\/div>\n<p>(protium)<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 136px\">1<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 136px\">1<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 136px\">0<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 136px\">1.0078<\/td>\n<td style=\"width: 78.25px;height: 136px;text-align: left\">99.989<\/td>\n<\/tr>\n<tr style=\"height: 136px\" valign=\"top\">\n<td style=\"width: 148.6875px;text-align: center;height: 136px\">[latex]_1^2\\text{H}[\/latex]<\/p>\n<div><\/div>\n<p>(deuterium)<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 136px\">1<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 136px\">1<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 136px\">1<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 136px\">2.0141<\/td>\n<td style=\"width: 78.25px;height: 136px;text-align: left\">0.0115<\/td>\n<\/tr>\n<tr style=\"height: 136px\" valign=\"top\">\n<td style=\"width: 148.6875px;text-align: center;height: 136px\">[latex]_1^3\\text{H}[\/latex]<\/p>\n<div><\/div>\n<p>(tritium)<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 136px\">1<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 136px\">1<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 136px\">2<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 136px\">3.01605<\/td>\n<td style=\"width: 78.25px;height: 136px;text-align: left\">\u2014 (trace)<\/td>\n<\/tr>\n<tr style=\"height: 24px\" valign=\"middle\">\n<td style=\"width: 62.21875px;text-align: center;height: 48px\" rowspan=\"2\">helium<\/td>\n<td style=\"width: 148.6875px;text-align: center;height: 24px\">[latex]_2^3\\text{He}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 24px\">2<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 24px\">2<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 24px\">1<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 24px\">3.01603<\/td>\n<td style=\"width: 78.25px;height: 24px;text-align: left\">0.00013<\/td>\n<\/tr>\n<tr style=\"height: 24px\" valign=\"top\">\n<td style=\"width: 148.6875px;text-align: center;height: 24px\">[latex]_2^4\\text{He}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 24px\">2<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 24px\">2<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 24px\">2<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 24px\">4.0026<\/td>\n<td style=\"width: 78.25px;height: 24px;text-align: left\">100<\/td>\n<\/tr>\n<tr style=\"height: 24px\" valign=\"middle\">\n<td style=\"width: 62.21875px;text-align: center;height: 48px\" rowspan=\"2\">lithium<\/td>\n<td style=\"width: 148.6875px;text-align: center;height: 24px\">[latex]_3^6\\text{Li}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 24px\">3<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 24px\">3<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 24px\">3<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 24px\">6.0151<\/td>\n<td style=\"width: 78.25px;height: 24px;text-align: left\">7.59<\/td>\n<\/tr>\n<tr style=\"height: 24px\" valign=\"top\">\n<td style=\"width: 148.6875px;text-align: center;height: 24px\">[latex]_3^7\\text{Li}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 24px\">3<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 24px\">3<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 24px\">4<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 24px\">7.0160<\/td>\n<td style=\"width: 78.25px;height: 24px;text-align: left\">92.41<\/td>\n<\/tr>\n<tr style=\"height: 24px\" valign=\"top\">\n<td style=\"width: 62.21875px;text-align: center;height: 24px\">beryllium<\/td>\n<td style=\"width: 148.6875px;text-align: center;height: 24px\">[latex]_4^9\\text{Be}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 24px\">4<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 24px\">4<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 24px\">5<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 24px\">9.0122<\/td>\n<td style=\"width: 78.25px;height: 24px;text-align: left\">100<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"middle\">\n<td style=\"width: 62.21875px;text-align: center;height: 96px\" rowspan=\"2\">boron<\/td>\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_5^{10}\\text{B}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">5<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">5<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">5<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">10.0129<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">19.9<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"top\">\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_5^{11}\\text{B}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">5<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">5<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">6<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">11.0093<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">80.1<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"middle\">\n<td style=\"width: 62.21875px;text-align: center;height: 144px\" rowspan=\"3\">carbon<\/td>\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_6^{12}\\text{C}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">6<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">6<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">6<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">12.0000<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">98.89<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"middle\">\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_6^{13}\\text{C}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">6<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">6<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">7<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">13.0034<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">1.11<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"top\">\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_6^{14}\\text{C}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">6<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">6<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">8<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">14.0032<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">\u2014 (trace)<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"middle\">\n<td style=\"width: 62.21875px;text-align: center;height: 96px\" rowspan=\"2\">nitrogen<\/td>\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_7^{14}\\text{N}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">7<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">7<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">7<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">14.0031<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">99.63<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"middle\">\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_7^{15}\\text{N}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">7<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">7<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">8<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">15.0001<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">0.37<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"middle\">\n<td style=\"width: 62.21875px;text-align: center;height: 144px\" rowspan=\"3\">oxygen<\/td>\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_8^{16}\\text{O}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">8<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">8<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">8<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">15.9949<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">99.757<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"middle\">\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_8^{17}\\text{O}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">8<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">8<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">9<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">16.9991<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">0.038<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"middle\">\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_8^{18}\\text{O}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">8<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">8<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">10<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">17.9992<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">0.205<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"middle\">\n<td style=\"width: 62.21875px;text-align: center;height: 48px\">fluorine<\/td>\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_9^{19}\\text{F}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">9<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">9<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">10<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">18.9984<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">100<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"middle\">\n<td style=\"width: 62.21875px;text-align: center;height: 144px\" rowspan=\"3\">neon<\/td>\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_{10}^{20}\\text{Ne}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">10<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">10<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">10<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">19.9924<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">90.48<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"middle\">\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_{10}^{21}\\text{Ne}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">10<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">10<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">11<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">20.9938<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">0.27<\/td>\n<\/tr>\n<tr style=\"height: 48px\" valign=\"middle\">\n<td style=\"width: 148.6875px;text-align: center;height: 48px\">[latex]_{10}^{22}\\text{Ne}[\/latex]<\/td>\n<td style=\"width: 46.21875px;text-align: center;height: 48px\">10<\/td>\n<td style=\"width: 43.109375px;text-align: center;height: 48px\">10<\/td>\n<td style=\"width: 51.046875px;text-align: center;height: 48px\">12<\/td>\n<td style=\"width: 54.234375px;text-align: center;height: 48px\">21.9914<\/td>\n<td style=\"width: 78.25px;height: 48px;text-align: left\">9.25<\/td>\n<\/tr>\n<tr style=\"height: 24px\">\n<td style=\"width: 519.765625px;height: 24px\" colspan=\"7\"><strong>Table 3.\u00a0<\/strong>Nuclear Compositions of Atoms of the Very Light Elements<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<div class=\"textbox shaded\">\n<h3 class=\"title\">Example 3<\/h3>\n<ol id=\"ball-ch03_s01_l05\" class=\"orderedlist\">\n<li>What is the symbol for an isotope of uranium that has an atomic number of 92 and a mass number of 235?<\/li>\n<li>How many protons and neutrons are in [latex]_{26}^{56}\\text{Fe}[\/latex]?<\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n<p class=\"simpara\"><strong>Solution<\/strong><\/p>\n<ol id=\"ball-ch03_s01_l06\" class=\"orderedlist\">\n<li>The symbol for this isotope is\u00a0[latex]_{92}^{235}\\text{U}[\/latex].<\/li>\n<li>This iron atom has 26 protons and 56 \u2212 26 = 30 neutrons.<\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n<p class=\"simpara\"><strong><em class=\"emphasis bolditalic\">Test Yourself<\/em><\/strong><\/p>\n<p id=\"ball-ch03_s01_p16\" class=\"para\">How many protons are in [latex]_{23}^{11}\\text{Na}[\/latex]?<\/p>\n<p>&nbsp;<\/p>\n<p class=\"simpara\"><strong><em class=\"emphasis\">Answer<\/em><\/strong><\/p>\n<p id=\"ball-ch03_s01_p17\" class=\"para\">11 protons<\/p>\n<\/div>\n<\/section>\n<section id=\"fs-idp42149200\">\n<div class=\"textbox shaded\">\n<h3 class=\"title\">Example 4<\/h3>\n<p class=\"Indent\"><span>Determine the number of protons, neutrons and electrons for the ion: <\/span><\/p>\n<p class=\"Indent\"><span>\u00a0<img loading=\"lazy\" decoding=\"async\" width=\"27\" height=\"24\" src=\"src\" alt=\"image\" \/><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/Screen-Shot-2018-05-03-at-12.54.51-PM.png\" alt=\"\" width=\"63\" height=\"49\" class=\"alignnone size-full wp-image-3379\" \/><\/span><\/p>\n<p class=\"Solution\"><strong>Solution\u00a0\u00a0 <\/strong><\/p>\n<p class=\"Indent\">The atomic number is 17, thus the ion contains 17 protons. The mass number is 35, therefore it contains 35 \u2013 17 = 18 neutrons. Because it is negatively charged (-1), it must have one more electron as compared to protons, thus 17 + 1 = 18 electrons.<\/p>\n<p>&nbsp;<\/p>\n<p class=\"SelfTest\"><strong>Test Yourself<\/strong><\/p>\n<p class=\"Indent\">Determine the number of electrons in each of the following ions. Hint: Use the periodic table to first determine the number of protons based on its elemental identity. \u00a0\u00a0a)<span>\u00a0 <\/span>Mg<sup>2+<\/sup><span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/span>b) Fe<sup>3+<\/sup><span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/span>c) O<sup>2-<\/sup><\/p>\n<p>&nbsp;<\/p>\n<p class=\"Answers\"><em><strong>Answers<\/strong><\/em><\/p>\n<p class=\"Answers\">a) 10<span>\u00a0\u00a0\u00a0 <\/span>b) 23<span>\u00a0\u00a0\u00a0<\/span>c) 10<\/p>\n<\/div>\n<\/section>\n<section id=\"fs-idp42149200\">\n<div class=\"textbox shaded\">\n<h3 class=\"title\">Example 5<\/h3>\n<p class=\"Indent\">Determine the number of protons, neutrons and electrons for the following atom, as well as its identity (chemical symbol) for: <span><img loading=\"lazy\" decoding=\"async\" width=\"28\" height=\"24\" src=\"src\" alt=\"image\" \/><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/Screen-Shot-2018-05-03-at-12.53.17-PM.png\" alt=\"\" width=\"62\" height=\"46\" class=\"alignnone size-full wp-image-3378\" \/><\/span><\/p>\n<p>&nbsp;<\/p>\n<p class=\"Solution\"><strong>Solution<\/strong><span><strong>\u00a0\u00a0<\/strong> <\/span><\/p>\n<p class=\"Indent\">The atomic number is 92 and mass number is 238. From the atomic number 92 we know that this must be Uranium (chemical symbol = U). The atomic number is equal to the number of protons, thus the number of protons is 92. Because the mass number is equal to the sum of the protons and neutrons, we know that n + 92 = 238. Thus, the number of neutrons is 238 \u2013 92 = 146. Finally, the given symbol must represent an atom, not an ion (no electric charge is shown) and any atom is neutral, thus the number of electrons must be the same as the number of protons, or 92 .<\/p>\n<p>&nbsp;<\/p>\n<p class=\"SelfTest\"><em><strong>Test Yourself<\/strong><\/em><\/p>\n<p class=\"Indentpoints\">a)<span>\u00a0 <\/span>Write the complete atomic symbol for krypton, which contains 48 neutrons\/<\/p>\n<p class=\"Indentpoints\">b)<span>\u00a0 <\/span>How many protons, neutrons and electrons are in <sup>132<\/sup>Cs?<\/p>\n<p>&nbsp;<\/p>\n<p class=\"Answers\"><em><strong>Answers<\/strong><\/em><\/p>\n<p class=\"Answers\">a) <sup>84<\/sup>Kr<span>\u00a0 <\/span>b) protons = 55, neutrons = 77, electrons = 55<\/p>\n<\/div>\n<\/section>\n<section id=\"fs-idp42149200\">\n<div id=\"fs-idm166072560\" class=\"textbox shaded\">\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/OSC_Interactive_200-1-2.png\" alt=\"\u00a0\" width=\"122\" height=\"76\" class=\"alignleft\" \/><\/p>\n<p id=\"fs-idm243168608\">Use this <a href=\"http:\/\/openstaxcollege.org\/l\/16PhetAtomBld\">Build an Atom simulator<\/a> to build atoms of the first 10 elements, see which isotopes exist, check nuclear stability, and gain experience with isotope symbols.<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<\/section>\n<section id=\"fs-idm54315440\">\n<h2>Atomic Mass<\/h2>\n<p id=\"fs-idp64485984\">Because each proton and each neutron contribute approximately one amu to the mass of an atom, and each electron contributes far less, the <strong>atomic mass<\/strong> of a single atom is approximately equal to its mass number (a whole number). However, the average masses of atoms of most elements are not whole numbers because most elements exist naturally as mixtures of two or more isotopes.<\/p>\n<p id=\"fs-idp249209552\">The mass of an element shown in a periodic table or listed in a table of atomic masses is a weighted, average mass of all the isotopes present in a naturally occurring sample of that element. This is equal to the sum of each individual isotope\u2019s mass multiplied by its fractional abundance.<\/p>\n<div class=\"equation\" id=\"fs-idm56955264\" style=\"text-align: center\">[latex]\\displaystyle{} \\text{average mass} = \\sum_{i} (\\text{fractional abundance} \\times \\text{isotopic mass})_{i}[\/latex]<\/div>\n<p id=\"fs-idp53715664\">For example, the element boron is composed of two isotopes: About 19.9% of all boron atoms are <sup>10<\/sup>B with a mass of 10.0129 amu, and the remaining 80.1% are <sup>11<\/sup>B with a mass of 11.0093 amu. The average atomic mass for boron is calculated to be:<\/p>\n<div class=\"equation\" id=\"fs-idp64426960\" style=\"text-align: center\">[latex]\\begin{array}{r @{{}={}} l} \\text{boron average mass} & (0.199 \\times 10.0129 \\;\\text{amu}) + (0.801 \\times 11.0093 \\;\\text{amu}) \\\\[1em] & 1.99 \\;\\text{amu} + 8.82 \\;\\text{amu} \\\\[1em] & 10.81 \\;\\text{amu} \\end{array}[\/latex]<\/div>\n<p id=\"fs-idm114336768\">It is important to understand that no single boron atom weighs exactly 10.8 amu; 10.8 amu is the average mass of all boron atoms, and individual boron atoms weigh either approximately 10 amu or 11 amu.<\/p>\n<div class=\"textbox shaded\" id=\"fs-idm139194256\">\n<h3>Example 6<\/h3>\n<p id=\"fs-idm202281808\">A meteorite found in central Indiana contains traces of the noble gas neon picked up from the solar wind during the meteorite\u2019s trip through the solar system. Analysis of a sample of the gas showed that it consisted of 91.84% <sup>20<\/sup>Ne (mass 19.9924 amu), 0.47% <sup>21<\/sup>Ne (mass 20.9940 amu), and 7.69% <sup>22<\/sup>Ne (mass 21.9914 amu). What is the average mass of the neon in the solar wind?<\/p>\n<p>&nbsp;<\/p>\n<p id=\"fs-idm194071296\"><strong>Solution<\/strong><\/p>\n<div class=\"equation\" id=\"fs-idm73306928\" style=\"text-align: center\">[latex]\\begin{array}{r @{{}={}} l} \\text{average mass} & (0.9184 \\times 19.9924 \\;\\text{amu}) + (0.0047 \\times 20.9940 \\;\\text{amu})+(0.0769 \\times 21.9914 \\;\\text{amu}) \\\\[1em] & (18.36+0.099+1.69) \\;\\text{amu} \\\\[1em] & 20.15 \\;\\text{amu} \\end{array}[\/latex]<\/div>\n<p id=\"fs-idm3186256\">The average mass of a neon atom in the solar wind is 20.15 amu. (The average mass of a terrestrial neon atom is 20.1796 amu. This result demonstrates that we may find slight differences in the natural abundance of isotopes, depending on their origin.)<\/p>\n<p>&nbsp;<\/p>\n<p id=\"fs-idm187119072\"><em><strong>Test Yourself<\/strong><\/em><br \/>\nA sample of magnesium is found to contain 78.70% of <sup>24<\/sup>Mg atoms (mass 23.98 amu), 10.13% of <sup>25<\/sup>Mg atoms (mass 24.99 amu), and 11.17% of <sup>26<\/sup>Mg atoms (mass 25.98 amu). Calculate the average mass of a Mg atom.<\/p>\n<p>&nbsp;<\/p>\n<p><em><strong>Answer<\/strong><\/em><\/p>\n<p>24.31 amu<\/p>\n<\/div>\n<p>We can also do variations of this type of calculation, as shown in the next example.<\/p>\n<div class=\"textbox shaded\" id=\"fs-idm233489360\">\n<h3>Example 7<\/h3>\n<p id=\"fs-idm170542656\">Naturally occurring chlorine consists of <sup>35<\/sup>Cl (mass 34.96885 amu) and <sup>37<\/sup>Cl (mass 36.96590 amu), with an average mass of 35.453 amu. What is the percent composition of Cl in terms of these two isotopes?<\/p>\n<p>&nbsp;<\/p>\n<p id=\"fs-idm111544320\"><strong>Solution<\/strong><br \/>\nThe average mass of chlorine is the fraction that is <sup>35<\/sup>Cl times the mass of <sup>35<\/sup>Cl plus the fraction that is <sup>37<\/sup>Cl times the mass of <sup>37<\/sup>Cl.<\/p>\n<div class=\"equation\" id=\"fs-idp1748832\" style=\"text-align: center\">[latex]\\text{average mass} = (\\text{fraction of} \\ ^{35}\\text{Cl} \\ \\times \\ \\text{mass of} \\ ^{35}\\text{Cl}) + (\\text{fraction of} \\ ^{37}\\text{Cl} \\ \\times \\ \\text{mass of} \\ ^{37}\\text{Cl})[\/latex]<\/div>\n<p id=\"fs-idp35897648\">If we let <em>x<\/em> represent the fraction that is <sup>35<\/sup>Cl, then the fraction that is <sup>37<\/sup>Cl is represented by 1.00 \u2212 <em>x<\/em>.<\/p>\n<p id=\"fs-idm78207296\">(The fraction that is <sup>35<\/sup>Cl + the fraction that is <sup>37<\/sup>Cl must add up to 1, so the fraction of <sup>37<\/sup>Cl must equal 1.00 \u2212 the fraction of <sup>35<\/sup>Cl.)<\/p>\n<p id=\"fs-idm174110736\">Substituting this into the average mass equation, we have:<\/p>\n<div class=\"equation\" id=\"fs-idm50612880\" style=\"text-align: center\">[latex]\\begin{array}{r @{{}={}} l}35.453 \\;\\text{amu} & (x \\times 34.96885 \\;\\text{amu}) + [(1.00 - x) \\times 36.96590\\;\\text{amu}] \\\\[1em] 35.453 & 34.96885x + 36.96590 - 36.96590x \\\\[1em] 1.99705x & 1.513 \\\\[1em] x & \\frac{1.513}{1.99705} = 0.7576 \\end{array}[\/latex]<\/div>\n<p id=\"fs-idm84424288\">So solving yields: <em>x<\/em> = 0.7576, which means that 1.00 \u2212 0.7576 = 0.2424. Therefore, chlorine consists of 75.76% <sup>35<\/sup>Cl and 24.24% <sup>37<\/sup>Cl.<\/p>\n<p>&nbsp;<\/p>\n<p id=\"fs-idm140620960\"><em><b>Test Yourself<\/b><\/em><\/p>\n<p>Naturally occurring copper consists of <sup>63<\/sup>Cu (mass 62.9296 amu) and <sup>65<\/sup>Cu (mass 64.9278 amu), with an average mass of 63.546 amu. What is the percent composition of Cu in terms of these two isotopes?<\/p>\n<p><em><strong>Answers<\/strong><\/em><\/p>\n<p>69.15% Cu-63 and 30.85% Cu-65<\/p>\n<\/div>\n<div id=\"fs-idm186474352\" class=\"textbox shaded\">\n<p><span id=\"fs-idm183783632\"> <img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/OSC_Interactive_200-1-2.png\" alt=\"\u00a0\" width=\"111\" height=\"69\" class=\"alignleft\" \/><\/span><\/p>\n<p id=\"fs-idp99251296\">Visit this <a href=\"http:\/\/openstaxcollege.org\/l\/16PhetAtomMass\">site<\/a> to make mixtures of the main isotopes of the first 18 elements, gain experience with average atomic mass, and check naturally occurring isotope ratios using the Isotopes and Atomic Mass simulation.<\/p>\n<\/div>\n<p id=\"fs-idp64386064\">The occurrence and natural abundances of isotopes can be experimentally determined using an instrument called a mass spectrometer. Mass spectrometry (MS) is widely used in chemistry, forensics, medicine, environmental science, and many other fields to analyze and help identify the substances in a sample of material. In a typical mass spectrometer (<a href=\"#CNX_Chem_02_03_MassSpec\" class=\"autogenerated-content\">Figure 5<\/a>), the sample is vaporized and exposed to a high-energy electron beam that causes the sample\u2019s atoms (or molecules) to become electrically charged, typically by losing one or more electrons. These cations then pass through a (variable) electric or magnetic field that deflects each cation\u2019s path to an extent that depends on both its mass and charge (similar to how the path of a large steel ball bearing rolling past a magnet is deflected to a lesser extent that that of a small steel BB). The ions are detected, and a plot of the relative number of ions generated versus their mass-to-charge ratios (a <em>mass spectrum<\/em>) is made. The height of each vertical feature or peak in a mass spectrum is proportional to the fraction of cations with the specified mass-to-charge ratio. Since its initial use during the development of modern atomic theory, MS has evolved to become a powerful tool for chemical analysis in a wide range of applications.<\/p>\n<figure id=\"CNX_Chem_02_03_MassSpec\">\n<figure style=\"width: 1300px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/opentextbc.ca\/chemistry\/wp-content\/uploads\/sites\/150\/2016\/05\/CNX_Chem_02_03_MassSpec.jpg\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/CNX_Chem_02_03_MassSpec-2.jpg\" alt=\"The left diagram shows how a mass spectrometer works, which is primarily a large tube that bends downward at its midpoint. The sample enters on the left side of the tube. A heater heats the sample, causing it to vaporize. The sample is also hit with a beam of electrons as it is being vaporized. Charged particles from the sample, called ions, are then accelerated and pass between two magnets. The magnetic field deflects the lightest ions most. The deflection of the ions is measured by a detector located on the right side of the tube. The graph to the right of the spectrometer shows a mass spectrum of zirconium. The relative abundance, as a percentage from 0 to 100, is graphed on the y axis, and the mass to charge ratio is graphed on the x axis. The sample contains five different isomers of zirconium. Z R 90, which has a mass to charge ratio of 90, is the most abundant isotope at about 51 percent relative abundance. Z R 91 has a mass to charge ratio of 91 and a relative abundance of about 11 percent. Z R 92 has a mass to charge ratio of 92 and a relative abundance of about 18 percent. Z R 94 has a mass to charge ratio of 94 and a relative abundance of about 18 percent. Z R 96, which has a mass to charge ratio of 96, is the least abundant zirconium isotope with a relative abundance of about 2 percent.\" width=\"1300\" height=\"606\" \/><\/a><figcaption class=\"wp-caption-text\"><strong>Figure 5.<\/strong> Analysis of zirconium in a mass spectrometer produces a mass spectrum with peaks showing the different isotopes of Zr.<\/figcaption><\/figure>\n<\/figure>\n<div id=\"fs-idm122264832\" class=\"textbox shaded\">\n<p><span id=\"fs-idm93902544\"> <img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/OSC_Interactive_200-1-2.png\" alt=\"\u00a0\" width=\"91\" height=\"56\" class=\"alignleft\" \/><\/span><\/p>\n<p id=\"fs-idm136290400\">See an <a href=\"http:\/\/openstaxcollege.org\/l\/16MassSpec\">animation<\/a> that explains mass spectrometry. Watch this <a href=\"http:\/\/openstaxcollege.org\/l\/16RSChemistry\">video<\/a> from the Royal Society for Chemistry for a brief description of the rudiments of mass spectrometry.<\/p>\n<\/div>\n<\/section>\n<section id=\"fs-idm131201632\" class=\"summary\">\n<h2>Key Concepts and Summary<\/h2>\n<p id=\"fs-idm148166800\">An atom consists of a small, positively charged nucleus surrounded by electrons. The nucleus contains protons and neutrons; its diameter is about 100,000 times smaller than that of the atom. The mass of one atom is usually expressed in atomic mass units (amu), which is referred to as the atomic mass. An amu is defined as exactly [latex]\\frac{1}{12}[\/latex] of the mass of a carbon-12 atom and is equal to 1.6605 \u00d7 10<sup>\u221224<\/sup> g.<\/p>\n<p id=\"fs-idp228494288\">Protons are relatively heavy particles with a charge of 1+ and a mass of 1.0073 amu. Neutrons are relatively heavy particles with no charge and a mass of 1.0087 amu. Electrons are light particles with a charge of 1\u2212 and a mass of 0.00055 amu. The number of protons in the nucleus is called the atomic number (Z) and is the property that defines an atom\u2019s elemental identity. The sum of the numbers of protons and neutrons in the nucleus is called the mass number and, expressed in amu, is approximately equal to the mass of the atom. An atom is neutral when it contains equal numbers of electrons and protons.<\/p>\n<p id=\"fs-idm194069072\">Isotopes of an element are atoms with the same atomic number but different mass numbers; isotopes of an element, therefore, differ from each other only in the number of neutrons within the nucleus. When a naturally occurring element is composed of several isotopes, the atomic mass of the element represents the average of the masses of the isotopes involved. A chemical symbol identifies the atoms in a substance using symbols, which are one-, two-, or three-letter abbreviations for the atoms.<\/p>\n<\/section>\n<section id=\"fs-idm7298256\" class=\"key-equations\">\n<h2>Key Equations<\/h2>\n<ul id=\"fs-idm175910672\">\n<li>[latex]\\displaystyle{} \\text{average mass} = \\sum_{i} (\\text{fractional abundance} \\times \\text{isotopic mass})_i[\/latex]<\/li>\n<\/ul>\n<div class=\"textbox exercises\">\n<h3 itemprop=\"educationalUse\">Exercises<\/h3>\n<p class=\"hanging-indent indent\">1. Write the symbol for each of the following ions:<\/p>\n<p id=\"fs-idp77154592\" class=\"hanging-indent indent\">a) the ion with a 1+ charge, atomic number 55, and mass number 133<\/p>\n<p id=\"fs-idm125607744\" class=\"hanging-indent indent\">b) the ion with 54 electrons, 53 protons, and 74 neutrons<\/p>\n<p id=\"fs-idm91510448\" class=\"hanging-indent indent\">c) the ion with atomic number 15, mass number 31, and a 3\u2212 charge<\/p>\n<p id=\"fs-idm78032064\" class=\"hanging-indent indent\">d) the ion with 24 electrons, 30 neutrons, and a 3+ charge<\/p>\n<p class=\"hanging-indent indent\">2. Open the <a href=\"http:\/\/openstaxcollege.org\/l\/16PhetAtomBld\">Build an Atom simulation<\/a> and click on the Atom icon.<\/p>\n<p id=\"fs-idm134679936\" class=\"hanging-indent indent\">a) Pick any one of the first 10 elements that you would like to build and state its symbol.<\/p>\n<p id=\"fs-idm125643536\" class=\"hanging-indent indent\">b) Drag protons, neutrons, and electrons onto the atom template to make an atom of your element.<\/p>\n<p class=\"hanging-indent indent\">State the numbers of protons, neutrons, and electrons in your atom, as well as the net charge and mass number.<\/p>\n<p id=\"fs-idm8547328\" class=\"hanging-indent indent\">c) Click on \u201cNet Charge\u201d and \u201cMass Number,\u201d check your answers to (b), and correct, if needed.<\/p>\n<p id=\"fs-idp210506208\" class=\"hanging-indent indent\">d) Predict whether your atom will be stable or unstable. State your reasoning.<\/p>\n<p id=\"fs-idp22922768\" class=\"hanging-indent indent\">e) Check the \u201cStable\/Unstable\u201d box. Was your answer to (d) correct? If not, first predict what you can do to make a stable atom of your element, and then do it and see if it works. Explain your reasoning.<\/p>\n<p class=\"hanging-indent indent\">3. Open the <a href=\"http:\/\/openstaxcollege.org\/l\/16PhetAtomBld\">Build an Atom simulation<\/a><\/p>\n<p id=\"fs-idm56609680\" class=\"hanging-indent indent\">a) Drag protons, neutrons, and electrons onto the atom template to make a neutral atom of Lithium-6 and give the isotope symbol for this atom.<\/p>\n<p id=\"fs-idm31990784\" class=\"hanging-indent indent\">b) Now remove one electron to make an ion and give the symbol for the ion you have created.<\/p>\n<p class=\"hanging-indent indent\">4. The following are properties of isotopes of two elements that are essential in our diet. Determine the number of protons, neutrons and electrons in each and name them.<\/p>\n<p id=\"fs-idp210102512\" class=\"hanging-indent indent\">a) atomic number 26, mass number 58, charge of 2+<\/p>\n<p id=\"fs-idp23141296\" class=\"hanging-indent indent\">b) atomic number 53, mass number 127, charge of 1\u2212<\/p>\n<p class=\"hanging-indent indent\">5. Give the number of protons, electrons, and neutrons in neutral atoms of each of the following isotopes:<\/p>\n<p id=\"fs-idm84436384\" class=\"hanging-indent indent\">a) [latex]_3^7\\text{Li}[\/latex]<\/p>\n<p id=\"fs-idm141443632\" class=\"hanging-indent indent\">b) [latex]_{52}^{125}\\text{Te}[\/latex]<\/p>\n<p id=\"fs-idm195681872\" class=\"hanging-indent indent\">c) [latex]_{47}^{109}\\text{Ag}[\/latex]<\/p>\n<p id=\"fs-idm82481216\" class=\"hanging-indent indent\">d) [latex]_{7}^{15}\\text{N}[\/latex]<\/p>\n<p id=\"fs-idm159280288\" class=\"hanging-indent indent\">e) [latex]_{15}^{31}\\text{P}[\/latex]<\/p>\n<p class=\"hanging-indent indent\">6. Average atomic masses listed by IUPAC are based on a study of experimental results. Bromine has two isotopes <sup>79<\/sup>Br and <sup>81<\/sup>Br, whose masses (78.9183 and 80.9163 amu) and abundances (50.69% and 49.31%) were determined in earlier experiments. Calculate the average atomic mass of bromine based on these experiments.<\/p>\n<p class=\"hanging-indent indent\">7. The average atomic masses of some elements may vary, depending upon the sources of their ores. Naturally occurring boron consists of two isotopes with accurately known masses (<sup>10<\/sup>B, 10.0129 amu and <sup>11<\/sup>B, 11.0931 amu). The average atomic mass of boron can vary from 10.807 to 10.819, depending on whether the mineral source is from Turkey or the United States. Calculate the percent abundances leading to the two values of the average atomic masses of boron from these two countries.<\/p>\n<p class=\"hanging-indent indent\">8. Explain Dalton&#8217;s atomic theory.<\/p>\n<p class=\"hanging-indent indent\">9. Which is larger, a proton or an electron?<\/p>\n<p class=\"hanging-indent indent\">10. Which is larger, a neutron or an electron?<\/p>\n<p class=\"hanging-indent indent\">11. What are the charges for each of the three subatomic particles?<\/p>\n<p class=\"hanging-indent indent\">12. Where is most of the mass of an atom located?<\/p>\n<p class=\"hanging-indent indent\">13. Sketch a diagram of a boron atom, which has five protons and six neutrons in its nucleus.<\/p>\n<p class=\"hanging-indent indent\">14. Define <em class=\"emphasis\">atomic number<\/em>. What is the atomic number for a boron atom?<\/p>\n<p class=\"hanging-indent indent\">15. Define <em class=\"emphasis\">isotope<\/em> and give an example.<\/p>\n<p class=\"hanging-indent indent\">16. What is the difference between deuterium and tritium?<\/p>\n<p class=\"hanging-indent indent\">17. Which pair represents isotopes?<\/p>\n<p class=\"indent hanging-indent\">a) \u00a0<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2015\/11\/13_a_question.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/13_a_question.png\" alt=\"13_a_question\" width=\"103\" height=\"37\" class=\"alignnone wp-image-4880\" \/><\/a><span class=\"inlineequation\">\u00a0 \u00a0 \u00a0 b)<sub> \u00a026<\/sub>F and <sub>25<\/sub>M \u00a0 \u00a0 \u00a0 \u00a0<\/span><span class=\"inlineequation\">c)<sub> \u00a014<\/sub>S and <sub>15<\/sub>P<\/span><\/p>\n<p class=\"indent hanging-indent\">18. \u00a0Which pair represents isotopes?<span class=\"inlineequation\">a) \u00a0<sub>20<\/sub>C<\/span>\u00a0and <sub>19<\/sub>K \u00a0 \u00a0 \u00a0<span class=\"inlineequation\">b)<sub> \u00a026<\/sub>F\u00a0and\u00a0<sub>27<\/sub>F \u00a0 \u00a0 \u00a0 \u00a0<\/span><span class=\"inlineequation\">c)<sub> \u00a092<\/sub>U<\/span>\u00a0and\u00a0<span class=\"inlineequation\"><sub>92<\/sub>U\u00a0 \u00a0 \u00a0d)\u00a0[latex]_7^{14}\\text{N}[\/latex]\u00a0and\u00a0[latex]_8^{14}\\text{N}[\/latex]\u00a0<\/span><\/p>\n<p class=\"indent hanging-indent\">19. \u00a0Give complete symbols of each atom, including the atomic number and the mass number.<\/p>\n<p class=\"indent hanging-indent\">a) \u00a0an oxygen atom with 8 protons and 8 neutrons<\/p>\n<p class=\"indent hanging-indent\">b) \u00a0a potassium atom with 19 protons and 20 neutrons<\/p>\n<p class=\"indent hanging-indent\">c) \u00a0a lithium atom with 3 protons and 4 neutrons<\/p>\n<p class=\"indent hanging-indent\"><span style=\"font-size: 1em\">20. \u00a0Give complete symbols of each atom, including the atomic number and the mass number.<\/span><\/p>\n<p>a) \u00a0a magnesium atom with 12 protons and 12 neutrons<\/p>\n<p>b) \u00a0a magnesium atom with 12 protons and 13 neutrons<\/p>\n<p>c) \u00a0a xenon atom with 54 protons and 77 neutrons<\/p>\n<p><span style=\"font-size: 1em\">21. \u00a0\u00a0 Americium-241 is an isotope used in smoke detectors. What is the complete symbol for this isotope?<\/span><\/p>\n<p><span style=\"font-size: 1em;text-indent: 2em\">22. \u00a0Carbon-14 is an isotope used to perform radioactive dating tests on previously living material. What is the complete symbol for this isotope?<\/span><\/p>\n<p><span style=\"font-size: 1em;text-indent: 2em\">23. \u00a0Give atomic symbols for each element.<\/span><\/p>\n<p>a) \u00a0sodium \u00a0 \u00a0\u00a0b) \u00a0argon \u00a0 \u00a0\u00a0c) \u00a0nitrogen \u00a0 \u00a0\u00a0d) \u00a0radon<\/p>\n<p><span style=\"font-size: 1em;text-indent: 2em\">24. \u00a0Give atomic symbols for each element.<\/span><\/p>\n<p>a) \u00a0silver \u00a0 \u00a0\u00a0b) \u00a0gold \u00a0 \u00a0 \u00a0c) \u00a0mercury \u00a0 \u00a0 \u00a0d) \u00a0iodine<\/p>\n<p><span style=\"font-size: 1em;text-indent: 2em\">25. \u00a0Give the name of the element.<\/span><\/p>\n<p>a) \u00a0Si \u00a0 \u00a0 \u00a0b) \u00a0Mn \u00a0 \u00a0 \u00a0c) \u00a0Fe \u00a0 \u00a0 \u00a0d) \u00a0Cr<\/p>\n<p><span style=\"font-size: 1em;text-indent: 2em\">26. \u00a0Give the name of the element.<\/span><\/p>\n<p>a) \u00a0F \u00a0 \u00a0 \u00a0b) \u00a0Cl \u00a0 \u00a0 \u00a0c) \u00a0Br \u00a0 \u00a0 \u00a0d) \u00a0I<\/p>\n<p>27.\u00a0Determine the atomic mass of each element, given the isotopic composition.<\/p>\n<p>a) \u00a0lithium, which is 92.4% lithium-7 (mass 7.016 u) and 7.60% lithium-6 (mass 6.015 u)<\/p>\n<p>b) \u00a0oxygen, which is 99.76% oxygen-16 (mass 15.995 u), 0.038% oxygen-17 (mass 16.999 u), and 0.205% oxygen-18 (mass 17.999 u)<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Answers<\/strong><\/p>\n<p id=\"fs-idm90412768\">1. (a) <sup>133<\/sup>Cs<sup>+<\/sup>; (b) <sup>127<\/sup>I<sup>\u2212<\/sup>; (c) <sup>31<\/sup>P<sup>3\u2212<\/sup>; (d) <sup>57<\/sup>Co<sup>3+<\/sup><\/p>\n<p id=\"fs-idm124722320\">2. (a) Carbon-12, <sup>12<\/sup>C; (b) This atom contains six protons and six neutrons. There are six electrons in a neutral <sup>12<\/sup>C atom. The net charge of such a neutral atom is zero, and the mass number is 12. (c) The preceding answers are correct. (d) The atom will be stable since C-12 is a stable isotope of carbon. (e) The preceding answer is correct. Other answers for this exercise are possible if a different element of isotope is chosen.<\/p>\n<p id=\"fs-idm134038192\">3. (a) Lithium-6 contains three protons, three neutrons, and three electrons. The isotope symbol is <sup>6<\/sup>Li or [latex]_3^6\\text{Li}[\/latex]. (b) <sup>6<\/sup>Li<sup>+<\/sup> or [latex]_3^6 \\text{Li}^+[\/latex]<\/p>\n<p id=\"fs-idm58517792\">4. (a) Iron, 26 protons, 24 electrons, and 32 neutrons; (b) iodine, 53 protons, 54 electrons, and 74 neutrons<\/p>\n<p id=\"fs-idm60087264\">5. (a) 3 protons, 3 electrons, 4 neutrons; (b) 52 protons, 52 electrons, 73 neutrons; (c) 47 protons, 47 electrons, 62 neutrons; (d) 7 protons, 7 electrons, 8 neutrons; (e) 15 protons, 15 electrons, 16 neutrons<\/p>\n<p id=\"fs-idm9833872\">6. 79.904 amu<\/p>\n<p id=\"fs-idm4806656\">7. Turkey source: 0.2649 (of 10.0129 amu isotope); US source: 0.2537 (of 10.0129 amu isotope)<\/p>\n<p>8. All matter is composed of atoms; atoms of the same element are the same, and atoms of different elements are different; atoms combine in whole-number ratios to form compounds.<\/p>\n<p>9.\u00a0A proton is larger than an electron.<br \/>\n10. A neutron is larger than an electron.<br \/>\n11. proton: 1+; electron: 1\u2212; neutron: 0<br \/>\n12. \u00a0Most of the mass of an atom is located in the nucleus.<\/p>\n<p><span style=\"font-size: 1em\">13.<\/span><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/09\/Nucleus.png\" style=\"font-size: 1em\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/chem1114langaracollege\/wp-content\/uploads\/sites\/387\/2018\/04\/Nucleus-1.png\" alt=\"Nucleus\" width=\"160\" height=\"160\" class=\"alignnone wp-image-4630\" \/><\/a><\/p>\n<p><span style=\"font-size: 1em\">14.\u00a0The atomic number is the number of protons in a nucleus. Boron has an atomic number of five.<\/span><\/p>\n<p><span style=\"font-size: 1em\">15.\u00a0Isotopes are atoms of the same element but with different numbers of neutrons.<\/span><\/p>\n<p><span style=\"font-size: 1em\">16. They are isotopes, therefore the difference between deuterium and tritium is the number of neutrons. \u00a0Deuterium has one, and tritium has two.<\/span><\/p>\n<p><span style=\"font-size: 1em\">17. (a)<\/span><\/p>\n<p><span style=\"font-size: 1em\">18.\u00a0 (b) &#8211; note: there is an error with option (d) for the atomic number of nitrogen can only be 7.<\/span><\/p>\n<p><span style=\"font-size: 1em\">19. \u00a0<\/span><span style=\"font-size: 1em\">a) [latex]_{8}^{16}\\text{O}[\/latex] \u00a0 \u00a0 \u00a0<\/span><span style=\"font-size: 1em\">b) \u00a0[latex]_{19}^{39}\\text{K}[\/latex] \u00a0 \u00a0 \u00a0c) \u00a0[latex]_{3}^{7}\\text{Li}[\/latex]<\/span><\/p>\n<p><span style=\"font-size: 1em\">20. \u00a0Give complete symbols of each atom, including the atomic number and the mass number.<\/span><\/p>\n<div class=\"question\">\n<p>a) \u00a0[latex]_{12}^{24}\\text{Mg}[\/latex] \u00a0 \u00a0 \u00a0b) \u00a0[latex]_{12}^{25}\\text{Mg}[\/latex] \u00a0 \u00a0 \u00a0c) \u00a0[latex]_{54}^{131}\\text{Xe}[\/latex]<\/p>\n<\/div>\n<div class=\"question\">\n<p id=\"ball-ch03_s01_qs01_p27\" class=\"para\">21. \u00a0\u00a0[latex]_{95}^{241}\\text{Am}[\/latex]<\/p>\n<\/div>\n<p><span style=\"font-size: 1em\">22. \u00a0[latex]_{6}^{14}\\text{C}[\/latex]<\/span><\/p>\n<p><span style=\"font-size: 1em\">23. \u00a0<\/span><span style=\"font-size: 1em\">a) \u00a0Na \u00a0 \u00a0 b) \u00a0Ar \u00a0 \u00a0 c) \u00a0N \u00a0 \u00a0\u00a0d) \u00a0Rn<\/span><\/p>\n<p><span style=\"font-size: 1em\">24. \u00a0a<\/span><span style=\"font-size: 1em\">) \u00a0Ag \u00a0 \u00a0 b) \u00a0Au \u00a0 \u00a0 \u00a0c) \u00a0Hg \u00a0 \u00a0 \u00a0d) \u00a0I<\/span><\/p>\n<p><span style=\"font-size: 1em\">25. \u00a0a<\/span><span style=\"font-size: 1em\">) \u00a0silicon \u00a0 \u00a0 \u00a0b) \u00a0manganese \u00a0 \u00a0 \u00a0c) \u00a0iron \u00a0 \u00a0 \u00a0d) \u00a0chromium<\/span><\/p>\n<p><span style=\"font-size: 1em\">26. \u00a0a<\/span><span style=\"font-size: 1em\">) \u00a0fluorine \u00a0 \u00a0 \u00a0b) \u00a0chlorine \u00a0 \u00a0 \u00a0c) \u00a0bromine \u00a0 \u00a0 \u00a0d) \u00a0iodine<\/span><\/p>\n<p>27. \u00a0a) \u00a06.940 u \u00a0 \u00a0\u00a0b) \u00a016.000 u<\/p>\n<\/div>\n<h2>Glossary<\/h2>\n<p><strong>electron:\u00a0<\/strong>negatively charged, subatomic particle of relatively low mass located outside the nucleus<\/p>\n<p><strong>anion:\u00a0<\/strong>negatively charged atom or molecule (contains more electrons than protons)<\/p>\n<p><strong>atomic mass:\u00a0<\/strong>average mass of atoms of an element, expressed in amu<\/p>\n<p><strong>atomic mass unit (amu):\u00a0<\/strong>(also, unified atomic mass unit, u, or Dalton, Da) unit of mass equal to [latex]\\frac{1}{12}[\/latex] of the mass of a <sup>12<\/sup>C atom<\/p>\n<p><strong>atomic number (Z):\u00a0<\/strong>number of protons in the nucleus of an atom<\/p>\n<p><strong>cation:\u00a0<\/strong>positively charged atom or molecule (contains fewer electrons than protons)<\/p>\n<p><strong>chemical symbol:\u00a0<\/strong>one-, two-, or three-letter abbreviation used to represent an element or its atoms<\/p>\n<p><strong>Dalton (Da):\u00a0<\/strong>alternative unit equivalent to the atomic mass unit<\/p>\n<p><strong>fundamental unit of charge:\u00a0<\/strong>(also called the elementary charge) equals the magnitude of the charge of an electron (e) with e = 1.602 \u00d7 10<sup>\u221219<\/sup> C<\/p>\n<p><strong>ion:\u00a0<\/strong>electrically charged atom or molecule (contains unequal numbers of protons and electrons)<\/p>\n<p><strong>isotopic mass:\u00a0<\/strong>mass of an isotope of an element, expressed in amu<\/p>\n<p><strong>mass number (A):\u00a0<\/strong>sum of the numbers of neutrons and protons in the nucleus of an atom<\/p>\n<p><strong>unified atomic mass unit (u):\u00a0<\/strong>alternative unit equivalent to the atomic mass unit<\/p>\n<\/section>\n","protected":false},"author":330,"menu_order":4,"template":"","meta":{"pb_show_title":"on","pb_short_title":"3.3 Atomic Structure and 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