Polyatomic Ions 

Acetate - C2H3O2 (-1 charge)

Ammonium - NH4 (+1 charge)

Bicarbonate - HCO3 (-1 charge)

Carbonate - CO3 (-2 charge)

Chlorate - CLO3 (-1 charge)

Chromate - CrO4 (-2 charge)

Hydroxide - OH (-1 charge)

Nitrate - NO3 (-1 charge)

Phosphate - PO4 (- 3 charge)

Sulfate - SO4 (-2 charge)

Arsenate- ASO4 (-3 charge)

Cyanide - CN (-1 charge)

Dichromate - Cr2O7 (-2 charge)

Nitrite- NO2 (-1 charge)

Oxalate - C204 (-2 charge)

Perchlorate- CLO4 (-1 charge)

Permanganate- MnO4 (-1 charge)

Sulfite- So3 (-2 charge)