Matching Pairs Common Polyatomic IonsOnline version Common Polyatomic Ions list from Chemistry - The Molecular Nature of Matter and Change - Third Canadian Edition by Maxwell Vonkeman 1 Cr2O7(2-) 2 SO4(2-) 3 ClO2(-) 4 HCO3(-) 5 O2(2-) 6 ClO3(-) 7 SO3(2-) 8 ClO4(-) 9 NO3(-) 10 PO4(3-) 11 CH3COO(-) 12 H3O(+) 13 HSO4(-) 14 NH4(+) 15 CN(-) 16 CO3(2-) 17 CrO4(2-) 18 ClO(-) 19 NO2(-) 20 Hg2(2+) 21 OH(-) 22 H2PO4(-) 23 MnO4(-) 24 HPO4(2-) Perchlorate Chlorite Hydrogen Phosphate Hydrogen sulfate/bisulfate Peroxide Nitrate Bicarbonate/Hydrogen Carbonate Mercury(I) Phosphate Carbonate Sulfate Cyanide Chlorate Hypochlorite Dihydrogen Phosphate Chromate Ammonium Dichromate Hydroxide Acetate Permanganate Hydronium Nitrite Sulfite