Polyatomic Ions - Groups of Atoms with a Charge

CHEMISTRY

Common Polyatomic Ions

Name Formula Name Formula

Ammonium NH4 +1 Acetate C2H3O2

-1

Chlorate ClO3 -1 Hydroxide OH -1

Nitrate NO3 -1 Nitrite NO2

-1

Carbonate CO3 -2 Sulfate SO4

-2

Sulfite SO3 -2 Phosphate PO4

-3

Formulas containing polyatomic ions are similar to formulas without them.

Characteristics of Polyatomic Ions The oxidation number of a polyatomic ion is its Charge.

Whenever a subscript is added to a polyatomic ion to make the total oxidation number in the formula equal zero, the ion MUST be enclosed with parenthesis, ( ).

the formula for a compound composed ofCalcium and Hydroxide Ion is Ca(OH)2

Parenthesis, ( ), are not used if no subscript is added.

the formula for a compound composed ofCalcium and Carbonate Ion is CaCO3

Write formulas for these:

Calcium Acetate Ammonium Phosphate Potassium Sulfate Aluminum Nitrate Copper (II) Chlorate Iron (III) Phosphate Barium Hydroxide Copper (I) Sulfite Mercury (III) Hydroxide Chromium (II) Acetate Tin (IV) Hydrogen Carbonate

Answers

Ca(C2H3O2)2 (NH4)3PO4 K2SO4 Al(NO3)3 Cu(ClO3)2 FePO4 Ba(OH)2 Cu2SO3 Hg(OH)3 Cr(C2H3O2)2 Sn(HCO3)4