1. Polyatomic Ions Polyatomic Ions are ions that are made up of many (poly) atoms (atomic). Polyatomic ions can be considered as “one ion”. E.g. HCO 3 -1 can be considered as “one anion”. E.g. NH 4 +1 can be considered as “one cation” Polyatomic ions form ionic compounds just like any othe r ion. E.g. K +1 + NO 3 -1 will form KNO 3 E.g. NH 4 +1 + SO 4 -2 will form (NH 4 ) 2 SO 4

2. These are named the same way as any other ionic compound. Remember, the Cation(+) always comes before the Anion(-). But Polyatomic ions have their own name, and do not ne ed an ending change. E.g. NO 3 -1 is a Nitrate ion. KNO 3 is Potassium Nitrate. (Not Potassium Nitride)

3. Can you write the chemical formula of these compounds? 1.Lead (II) Sulfate 2.Barium Sulfate 3.Sodium Acetate 4.Potassium Sulfate 5.Ammonium Iodide PbSO 4 BaSO 4 NaC 2 H 3 O 2 K 2 SO 4 NH 4 I