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Chapter 6 Lecture Basic Chemistry Fourth Edition 6.2 Writing Formulas and Naming Ionic Compounds Learning Goal Using charge balance, write the correct formula for an ionic compound. © 2014 Pearson Education, Inc. Catalyst 10/21: Periodic Table Activity © 2014 Pearson Education, Inc. Properties of Ionic Compounds The physical and chemical properties of elements change when they react to form ionic compounds. © 2014 Pearson Education, Inc. Chemical Formulas of Ionic Compounds The chemical formula of a compound represents the symbols and numbers of atoms or ions in the lowest whole-number ratio. The sum of the ionic charges is always zero. © 2014 Pearson Education, Inc. Subscripts in Formulas Two chlorine atoms are needed to react with one magnesium atom to give the compound magnesium chloride (MgCl2) charge balance. Subscripts in an ionic compound represent the lowest number of positive and negative ions that give an overall charge of zero. © 2014 Pearson Education, Inc. Writing Ionic Formulas from Ionic Charges To write the formula of a compound that contains Na+ and S2− •metal ions are written first, followed by an ion from a nonmetal •two Na+ ions needed for charge balance are represented using a subscript in the formula •the subscript for the nonmetal S2− is 1 (it is understood and not written in the formula) © 2014 Pearson Education, Inc. Learning Check Use charge balance to write the formula for lithium nitride, a compound containing Li+ and N3−. © 2014 Pearson Education, Inc. Solution Use charge balance to write the formula for lithium nitride, a compound containing Li+ and N3−. © 2014 Pearson Education, Inc. Learning Check Use charge balance to write the ionic formula of the compound containing Ba2+ and Cl−. © 2014 Pearson Education, Inc. Solution Use charge balance to write the ionic formula of the compound containing Ba2+ and Cl−. © 2014 Pearson Education, Inc. Learning Check Select the correct formula for each of the following ionic compounds: A. Li+ and O2− (1) LiO (2) Li2O (3) LiO2 B. Al3+ and Cl− (1) AlCl3 (2) AlCl (3) Al3Cl C. Mg2+ and N3− (1) MgN (2) Mg2N3 (3) Mg3N2 © 2014 Pearson Education, Inc. Solution Select the correct formula for each of the following ionic compounds: A. Li+ and O2− (2) Li2O B. Al3+ and Cl− (1) AlCl3 C. Mg2+ and N3− (3) Mg3N2 © 2014 Pearson Education, Inc. Naming Ionic Compounds The name of an ionic compound has two components: • the name of the metal ion which is written first and is the same as its elemental name • the name of the nonmetal ion which is written last by using the first syllable of its element name followed by ide A space separates the name of the metal and nonmetal. © 2014 Pearson Education, Inc. Names of Some Ionic Compounds © 2014 Pearson Education, Inc. Guide to Naming Ionic Compounds with Metals That Form a Single Ion © 2014 Pearson Education, Inc. Naming Ionic Compounds, Metal Forms a Single Ion Write the name of an ionic compound with the formula Mg3N2. Step 1 Identify the cation and anion. The cation from Group 2A (2) is Mg2+, and the anion from Group 5A (15) is N3−. Step 2 Name the cation by its element name. The cation Mg2+ is magnesium. © 2014 Pearson Education, Inc. Naming Ionic Compounds, Metal Forms a Single Ion Write the name of an ionic compound with the formula Mg3N2. Step 3 Name the anion by using the first syllable of its element name followed by ide. The anion N3− is nitride. Step 4 Write the name for the cation first and the name for the anion second. Mg3N2 is magnesium nitride. © 2014 Pearson Education, Inc. Learning Check Select the correct name for each of the following ionic compounds. A. CaS (1) calcium sulfur (2) calcide sulfur (3) calcium sulfide B. K2O (1) dipotassium oxide (2) potassium oxide (3) potassium oxygen © 2014 Pearson Education, Inc. Solution Select the correct name for each of the following ionic compounds. A. CaS (3) calcium sulfide B. K2O © 2014 Pearson Education, Inc. (2) potassium oxide