Anions Acetate (ethanoate) CH 3COO− or C 2H 3O− 2 Acetylide C2− 2 Benzoate C 6H 5COO− or C 7H 5O− 2 Carbonate CO2− 3 Chromate CrO2− 4 Citrate C 6H 5O3− 7 Cyanide CN− Hypochlorite ClO− Chlorite ClO− 2 Chlorate ClO− 3 Perchlorate ClO− 4 Dichromate Cr 2O2− 7 Dihydrogen phosphate H 2PO− 4 Hydrogen carbonate (bicarbonate) HCO− 3 Hydrogen sulfate (bisulfate) HSO− 4 Hydrogen phosphate HPO2− 4 Hydroxide OH− Nitrite NO− 2 Nitrate NO− 3 Peroxide O2− 2 Permanganate MnO− 4 Phosphate PO3− 4 Sulfite SO2− 3 Sulfate SO2− 4