Some Common Polyatomic Ions

Ammonium NH4+ Chlorate ClO3- Peroxide O2-2
Acetate CH3COO- Perchlorate ClO4- Chromate CrO4-2
Nitrate NO3- Permanganate MnO4- Dichromate Cr2O7-2
Nitrite NO2- Carbonate CO3-2 Silicate SiO3-2
Hydroxide OH- Sulfate SO4-2 Phosphate PO4-3
Hypochlorite ClO- Sulfite SO3-2 Arsenate AsO4-3
Chlorite ClO2- Thiosulfate S2O3-2 Arsenite AsO3-3
Cyanate CN- Thiocyanate SCN- Borate BO3-3
Bicarbonate HCO3- Bisulfate HSO4- Bisulfite HSO3-