1. Ionic Bonding  Electrons are transferred  Electronegativity differences are generally greater than 1.7  The formation of ionic bonds is always exothermic!

2. Determination of Ionic Character Compounds are ionic if they conduct electricity in their molten state Electronegativity difference is not the final determination of ionic character

3. Coulomb’s Law “The energy of interaction between a pair of ions is proportional to the product of their charges, divided by the distance between their centers”

4. Table of Ion Sizes

5. Estimate  H f for Sodium Chloride Na(s) + ½ Cl 2 (g)  NaCl(s) Na(s)  Na(g) + 109 kJ Na(g)  Na + (g) + e - + 495 kJ ½ Cl 2 (g)  Cl(g) + ½(239 kJ) Cl(g) + e -  Cl - (g) - 349 kJ Na + (g) + Cl - (g)  NaCl(s) -786 kJ Na(s) + ½ Cl 2 (g)  NaCl(s) -412 kJ/mol

6. Estimate  H f for Magnesium Fluoride Mg (s) + F 2(g)  MgF 2(s) Mg(s)  Mg(g) + 150 kJ Mg(g)  Mg 2+ (g) + 2e - +735 + 1445 kJ F 2 (g)  2F(g) +154kJ 2F(g) + 2e -  2F - (g) 2(- 328)kJ Mg 2+ (g) + 2F - (g)  MgF 2(s ) -3916kJ Mg(s) + F 2 (g)  MgF 2 (s) -2088 kJ/mol

7. Sodium Chloride Crystal Lattice Ionic compounds form solid crystals at ordinary temperatures. Ionic compounds organize in a characteristic crystal lattice of alternating positive and negative ions. All salts are ionic compounds and form crystals.

8. Properties of Ionic Compounds