polyatomic ions

• acetate

  C2H3O 2-
• carbonate

  CO3 2-
• hydrogen carbonate

  HCO3 -
• hydroxide

  OH -
• nitrite

  NO2 -
• nitrate

  NO3 -
• chromate

  CrO4 2-
• dichromate

  Cr2O7 2-
• phosphate

  PO4 3-
• hydrogen phosphate

  HPO4 2-
• dihydrogen phosphate

  H2PO4 -
• ammonium

  NH4 +
• hypochlorite

  ClO -
• chlorite

  ClO2 -
• chlorate

  ClO3 -
• perchlorate

  ClO4 -
• permanganate

  MnO4 -
• sulfate

  SO4 2-
• hydrogen sulfate

  HSO4 -
• cyanide

  CN -
• peroxide

  O2 2-