polyatomic anions

carbonate

$$CO3^{2-}$$

bicarbonate

$$HCO3^{-}$$

nitrate

$$NO3^{-}$$

nitrite

$$NO2^{-}$$

phosphate

$$PO4^{3-}$$

hydrogen phosphate

$$HPO4^{2-}$$

dihydrogen phosphate

$$H2PO4^{-}$$

chromate

$$CrO4^{2-}$$

dichromate

$$Cr2O_7^{2-}$$

acetate

$$C_2H_3O_2^{-}$$

thiocyanate

$$SCN^{-}$$

sulfate

$$SO_4^{2-}$$

hydrogen sulfate

$$HSO_4^{-}$$

sulfite

$$SO_3^{2-}$$

hydrogen sulfite

$$HSO_3^{-}$$

Permanganate

$$MnO_4^{-}$$

hypochlorite

$$ClO^{-}$$

chlorite

$$ClO_2^{-}$$

chlorate

$$ClO_3^{-}$$

perchlorate

$$ClO_4^{-}$$

oxalate

$$C_2O_4^{2-}$$

Thiosulfate

$$S_2O_3^{2-}$$