General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake 5.2 Ionic Compounds Chapter 5 Compounds and Their Bonds © 2013 Pearson Education, Inc. Lectures

© 2013 Pearson Education, Inc. Chapter 5, Section 2 2 Ionic compounds  consist of positive and negative ions.  have attractive forces between the positive and negative ions called ionic bonds.  have high melting and boiling points.  are solid at room temperature. Ionic Compounds

© 2013 Pearson Education, Inc. Chapter 5, Section 2 3 Salt Is an Ionic Compound Sodium chloride, or “table salt,” is an example of an ionic compound.

© 2013 Pearson Education, Inc. Chapter 5, Section 2 4 Formulas of Ionic Compounds The chemical formula of an ionic compound represents the element symbols and subscripts, which represent the lowest whole-number ratio of ions. In the formula of an ionic compound,  the sum of positively and negatively charged ions is always zero.  the charges are balanced.

© 2013 Pearson Education, Inc. Chapter 5, Section 2 5 Charge Balance for NaCl, “Salt” In NaCl,  a Na atom loses its valence electron.  a Cl atom gains an electron.  the symbol of the metal (sodium) is written first, followed by the symbol of the nonmetal (chlorine).

© 2013 Pearson Education, Inc. Chapter 5, Section 2 6 Charge Balance In MgCl 2 In MgCl 2,  a Mg atom loses two valence electrons.  two Cl atoms gain one electron each.  subscripts indicate the number of ions needed to give charge balance.  the symbol of the metal (magnesium) is written first, followed by the symbol of the nonmetal (chlorine).

© 2013 Pearson Education, Inc. Chapter 5, Section 2 7 Writing Ionic Formulas from Charge Balance Charge balance is used to write the formula for sodium nitride, a compound containing Na + and N 3−.

© 2013 Pearson Education, Inc. Chapter 5, Section 2 8 Charge Balance in Na 2 S In sodium sulfide, Na 2 S,  two Na atoms lose one valence electron each.  one S atom gains two electrons.  subscripts show the number of ions needed to give charge balance. The group of ions with the lowest ratio of ions in an ionic compound is called a formula unit.

© 2013 Pearson Education, Inc. Chapter 5, Section 2 9 Formula from Ionic Charges Write the ionic formula of the compound containing Ba 2+ and Cl −.  Write the symbols of each ion. Ba 2+ Cl −  Balance the charges. Ba 2+ Cl − (two Cl  needed) Cl −  Write the metal first, followed by the nonmetal,, using a subscript to represent the number of. Cl − ions. BaCl 2

© 2013 Pearson Education, Inc. Chapter 5, Section 2 10 Select the correct formula for each of the following ionic compounds. 1. Na + and S 2– A. NaS B. Na 2 SC. NaS 2 2. Al 3+ and Cl – A. AlCl 3 B. AlCl C. Al 3 Cl 3. Mg 2+ and N 3– A. MgN B. Mg 2 N 3 C. Mg 3 N 2 Learning Check

© 2013 Pearson Education, Inc. Chapter 5, Section 2 11 Select the correct formula for each of the following ionic compounds. 1. Na + and S 2– B. Na 2 S 2. Al 3+ and Cl – A. AlCl 3 3. Mg 2+ and N 3– C. Mg 3 N 2 Solution