1 Chapter 5 Ionic Compounds 5.2 Ionic Compounds Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

2 Ionic compounds Consist of positive and negative ions. Have ionic bonds between positively and negatively charged ions. Have high melting and boiling points. Are solid at room temperature. Ionic Compounds

3 Salt is An Ionic Compound Sodium chloride (table salt) is an example of an ionic compound. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

4 An ionic formula Consists of positively and negatively charged ions. Is neutral. Has charge balance. total positive charge = total negative charge Uses subscripts to indicate the number of ions needed to give charge balance. Ionic Formulas

5 Ionic Formula of NaCl In an ionic formula The symbol of the metal is written first followed by the symbol of the nonmetal. The charges of the ions in the compound are not shown. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

6 The formulas of ionic compounds are determined from the charges on the ions. atoms ions     – Na  +  F :  Na + : F :  NaF     sodium fluorine sodium fluoride The overall charge of NaF is zero (0). Na + F - = NaF (1+ ) + (1-) = 0 Charge Balance in NaF

7 Charge Balance In MgCl 2 In forming MgCl 2 A Mg atom loses two valence electrons. Two Cl atoms each gain one electron. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

8 Writing Ionic Formulas from Charges Charge balance is used to write the formula for sodium nitride, a compound containing Na + and N 3−. Na + 3Na + N 3− = Na 3 N Na + 3(+1) + 1(3-) = 0

9 Write the ionic formula of the compound with Ba 2+ and Cl . Write the symbols of the ions. Ba 2+ Cl  Balance the charges. Ba 2+ Cl  two Cl - needed Cl  Write the ionic formula using a subscript 2 for two chloride ions. BaCl 2 Formula from Ionic Charges

10 Write the correct formula for the ionic compounds formed by the following ions: A. Na + and S 2- 1) NaS 2) Na 2 S3) NaS 2 B. Al 3+ and Cl - 1) AlCl 3 2) AlCl 3) Al 3 Cl C. Mg 2+ and N 3- 1) MgN 2) Mg 2 N 3 3) Mg 3 N 2 Learning Check

11 A. Na + and S 2- 2) Na 2 S B. Al 3+ and Cl - 1) AlCl 3 C. Mg 2+ and N 3- 3) Mg 3 N 2 Solution