Chapter 3 Lecture Outline PDF

Chapter 3 Lecture Outline Prepared by JAN HENRI G. CARPIZO, RMT University of Pangasinan 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for repr...

Chapter 3 Lecture Outline Prepared by JAN HENRI G. CARPIZO, RMT University of Pangasinan 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.  3.1 Introduction to Bonding Bonding is the joining of two atoms in a stable arrangement. Elements will gain, lose, or share electrons to reach the electron configuration of the noble gas closest to them in the periodic table. There are two different kinds of bonding: 1. Ionic bonds result from the transfer of electrons from one element to another. 2. Covalent bonds result from the sharing of electrons between two atoms. 2  3.1 Introduction to Bonding Ionic bonds form between: A metal on the left side of the periodic table. A nonmetal on the right side of the periodic table. 3  3.1 Introduction to Bonding Covalent bonds are formed when two nonmetals combine, or when a metalloid bonds to a nonmetal. A molecule is a discrete group of atoms that share electrons. 4  3.2 Ions A. Cations and Anions Ions are charged species in which the number of protons and electrons in an atom is unequal. Ionic compounds consist of oppositely charged ions that have a strong electrostatic attraction for each other. There are two types of ions—cations and anions. 5  3.2 Ions A. Cations and Anions Cations are positively charged ions. A cation has fewer electrons (e−) than protons. the sodium atom the sodium ion 6  3.2 Ions A. Cations and Anions By losing one, two, or three e−, an atom forms a cation with a completely filled outer shell of e−. the magnesium atom the magnesium ion 7  3.2 Ions A. Cations and Anions Anions are negatively charged ions. An anion has more e− than protons. the chlorine atom the chlorine ion 8  3.2 Ions A. Cations and Anions By gaining one, two, or three electrons, an atom forms an anion with a completely filled outer shell of e−. The octet rule: a main group element is especially stable when it possesses an octet of e− in its outer shell. octet = 8 valence e− 9  3.2 Ions B. Relating Group Number to Ionic Charge for Main Group Elements Elements in the same group form ions of similar charge. Metals form cations. For metals in groups 1A, 2A, and 3A, the group number = the charge on the cation. Nonmetals form anions. For nonmetals in Groups 6A and 7A, the anion charge = 8 – the group number. 10  3.2 Ions B-1 Relating Group Number to Ionic Charge for Groups 1A–3A the cation charge = the group number group 1A: M M+ + e − 1 valence e− group 2A: M M2+ + 2e− 2 valence e− group 3A: M M3+ + 3e− 3 valence e− 11  3.2 Ions B-2 Relating Group Number to Ionic Charge for Groups 6A and 7A the anion charge = 8 – group number group 6A: X + 2e− X 2− 6 valence e− charge = 8 – 6 = 2 group 7A: X + e− X − 7 valence e− charge = 8 – 7 = 1 12 3.2 Ions 13  3.2 Ions C. Metals with Variable Charge 14  3.2 Ions D. Common Ions in the Human Body 15  3.3 Ionic Compounds The sum of the charges in an ionic compound must be zero overall. 16 3.3 Ionic Compounds 17  3.3 Ionic Compounds HOW TO Write a Formula for an Ionic Compound Step Identify which element is the cation and which is the anion. Metals form cations and nonmetals form anions. Use the group number of a main group element to determine the charge. K+ Cl− Ca2+ O2− metal nonmetal metal nonmetal group 1A group 7A group 2A group 6A 18  3.3 Ionic Compounds HOW TO Write a Formula for an Ionic Compound Step Determine how many of each ion type is needed for an overall charge of zero. When the cation and anion have the same charge, only one of each is needed. K+ + Cl− KCl Ca2+ + O2− CaO zero charge zero charge One of each ion is needed to balance charge. 19  3.3 Ionic Compounds HOW TO Write a Formula for an Ionic Compound When the cation and anion have different charges, use the ion charges to determine the number of ions of each needed. Ca2+ Cl− A +2 charge means A -1 charge means 2 Cl− anions are 1 Ca2+ cation is needed. needed. Ca2+ + Cl− CaCl2 2 Cl− for each Ca2+ 20  3.3 Ionic Compounds HOW TO Write a Formula for an Ionic Compound Step To write the formula, place the cation first and then the anion, and omit charges. Examples: KCl CaO CaCl2 Use subscripts to show the number of each ion needed to have a zero overall charge. When no subscript is written, it is assumed to be “1.” 21  3.4 Naming Ionic Compounds A. Naming Cations Main group cations are named for the element from which they are formed. Na+ K+ Ca2+ Mg2+ sodium potassium calcium magnesium 22  3.4 Naming Ionic Compounds A. Naming Cations Other cations can be named two ways: Systematic name: Follow the name of the cation by a Roman numeral in parentheses to indicate its charge. Fe2+ Fe3+ iron(II) iron(III) 23  3.4 Naming Ionic Compounds A. Naming Cations Other cations can be named two ways: Common name: Use suffix “-ous” for the cation with a smaller charge and suffix “-ic” for the cation with a higher charge. Fe2+ Fe3+ ferrous ferric 24 3.4 Naming Ionic Compounds A. Naming Cations 25  3.4 Naming Ionic Compounds B. Naming Anions Anions are named by replacing the ending of the element name by the suffix “-ide.” 26  3.4 Naming Ionic Compounds C. Compounds of Main Group Metals Name the cation and then the anion. Do not specify the charge on the ion. Do not specify how many ions of each type are needed to balance charge. Na+ + F− NaF sodium fluoride sodium fluoride Mg2+ + Cl− MgCl2 magnesium chloride magnesium chloride 27  3.4 Naming Ionic Compounds D. Compounds of Metals with a Variable Charge HOW TO Name an Ionic Compound That Contains a Metal with Variable Charge Example Give the name for CuCl2. Step Determine the charge on the cation. 2 Cl− anions = −2 total negative charge CuCl2 Cu cation must have a +2 charge to make the overall charge zero 28  3.4 Naming Ionic Compounds D. Compounds of Metals with a Variable Charge HOW TO Name an Ionic Compound That Contains a Metal with Variable Charge Step Name the cation and the anion. The cation is named one of two possible ways: Systematic Common Cu2+ copper(II) cupric The anion changes ending of element name to “-ide” Cl− chloride 29  3.4 Naming Ionic Compounds D. Compounds of Metals with a Variable Charge HOW TO Name an Ionic Compound That Contains a Metal with Variable Charge Write the name of the cation first, then Step the anion. copper(II) chloride Answer = or cupric chloride 30  3.4 Naming Ionic Compounds E. Writing a Formula from the Name HOW TO Derive a Formula from the Name of an Ionic Compound Example Write the formula for tin(IV) oxide. Step Identify the cation and anion and determine their charges. tin(IV) oxide Sn4+ O2− 31  3.4 Naming Ionic Compounds E. Writing a Formula from the Name HOW TO Derive a Formula from the Name of an Ionic Compound Step Balance charges. Two −2 anions Sn4+ O2− are needed for each +4 cation. Step Write the formula with the cation first, and use subscripts to show how many of each ion is needed to have zero overall charge. final answer = SnO2 32 3.5 Physical Properties of Ionic Compounds Ionic compounds are crystalline solids with very high melting and boiling points. When ionic compounds dissolve in water, they separate into cations and anions, increasing the conductivity of the solution. + 🡪 NaCl water solution 33  3.6 Polyatomic Ions A polyatomic ion is a cation or anion that contains more than one atom. 34  3.6 Polyatomic Ions A. Writing Formulas for Ionic Compounds with Polyatomic Ions When a cation and anion of equal charge combine, only one of each ion is needed. Na+ + NO2− NaNO2 zero overall charge Ba2+ + SO42− BaSO4 zero overall charge 35  3.6 Polyatomic Ions A. Writing Formulas for Ionic Compounds with Polyatomic Ions When a cation and anion of unequal charge combine, use the ionic charges to determine the relative number of each ion that is needed. Mg2+ + OH− Mg(OH)2 +2 charge means −1 charge means zero overall 2 OH− anions are 1 Mg2+ anion is charge needed. needed. 36  3.6 Polyatomic Ions B. Naming Ionic Compounds with Polyatomic Ions The same rules are followed for naming standard ionic compounds: Name the cation and then the anion. Do not specify the charge on the ions. Do not specify how many ions of each type are needed to balance charge. NaHCO3 Al2(SO4)3 sodium bicarbonate aluminum sulfate 37