The main "need-to-know" polyatomic ions that don't follow the Nomenclature rules for ions.
Acetate
C2H3O2^-1
Carbonate
CO3^-2
Hydrogen Carbonate (Bicarbonate)
HCO3^-1
Hydroxide
OH^-1
Nitrite
NO2^-1
Nitrate
NO3^-1
Chromate
CrO4^-2
Dichromate
Cr2O7^-2
Phosphate
PO4^-3
Hydrogen Phosphate
HPO4^-2
Dihydrogen Phosphate
H2PO4^-1
Ammonium
NH4^+1
Hypochlorite
ClO^-1
Chlorite
ClO2^ -1
Chlorate
ClO3^-1
Perchlorate
ClO4^-1
Permanganate
MnO4^-1
Sulfite
SO3^-2
Hydrogen Sulfite (Bisulfite)
HSO3^-1
Sulfate
SO4^-2
Hydrogen Sulfate (Bisulfate)
HSO4^-1
Cyanide
CN^-1
Peroxide
O2^-2