22 polyatomic ions

Acetate

C3H3O2(1-)

Hypochlorite

CIO(1-)

Chlorite

CIO2(1-)

Chlorate

CIO3(1-)

Perchlorate

CIO4(1-)

Cyanide

CN(1-)

Carbonate

CO3(2-)

Dichromate

Cr2O7(2-)

Chromate

CrO4(2-)

Dihydrogen phosphate

H2PO4(1-)

Hydrogen carbonate

HCO3(2-)

Hydrogen phosphate

HPO4(2-)

Hydrogen sulfate

HSO4(1-)

Permanganate

MnO4(1-)

Ammonium

NH4(1+)

Nitrite

NO2(1-)

Nitrate

NO3(1-)

Peroxide

O2(2-)

Hydroxide

OH(1-)

Phosphate

PO4(3-)

Sulfite

SO3(1-)

Sulfate

SO4(2-)