 Objectives  Derive formula units based on the charges of ions.  Name binary ionic compounds.

Chemical Formula Al 2 (SO 4 ) 3

Formula Units for Binary Ionic Compounds  Write symbols side by side with the cation first  Cross over the absolute value of charges to opposite subscript  Check to make sure compound is neutral and simplify to lowest whole number ratio

Sample Problem  Write the formula for a compound that contains Al 3+ and O 2-

Practice, p. 223 & Ck Answers

Practice, p. 223, cont.

Naming Binary Ionic Compounds  Name cation first and then name anion, giving it -ide ending  Name a compound composed of magnesium and chlorine

Stock System  Uses Roman numeral to indicate an ion’s charge (or oxidation state)  Numeral is enclosed in parentheses and written immediately after metal name with no space  Name a compound composed of Cu 2+ and Cl -

Practice, p. 225 & Ck Answers

Practice, p. 225, cont.

Compounds with Polyatomic Ions  Most are negatively charged  Many are oxyanions (contain oxygen)  Ion with greater number of oxygen atoms -ate NO 3 - nitrate  Ion with smaller number oxygen atoms -ite NO 2 - nitrite  If one fewer oxygen than –ite, it has hypo- prefix  If one more oxygen than –ate, it has per- prefix

More Oxyanions  ClO - hypochlorite  ClO 2 - chlorite  ClO 3 - chlorate  ClO 4 - perchlorate

Naming Compounds with Polyatomic Ions  Cation first followed by name of anion  Sample Problem  Write the formula for tin(IV) sulfate

Practice, p. 227 & Check Answers

Practice, p. 227, cont.