common polyatomic ions

ammonium

NH4(+)

nitrite

NO2(-)

nitrate

NO3(-)

sulfite

SO3(2-)

sulfate

SO4(2-)

hydrogen sulfate

HSO4(-)

hydroxide

OH(-)

cyanide

CN(-)

phosphate

PO4(3-)

hydrogen phosphate

HPO4(2-)

dihydrogen phosphate

H2PO4(-)

carbonate

CO3(2-)

hydrogen carbonate

HCO3(-)

hypochlorite

ClO(-)

chlorite

ClO2(-)

chlorate

ClO3(-)

perchlorate

ClO4(-)

acetate

C2H3O2(-)

permanganate

MnO4(-)

dichromate

Cr2O7(2-)

chromate

CrO4(2-)

peroxide

O2(2-)