Common Polyatomics

monovalent polyatomic cations (+1 charge): 

divalent polyatomic anions (-2 charge): 

H₃O⁺ hydronium 

CrO₄^-2 chromate 

NH₄⁺ ammonium 

Cr₂O₇^-2 dichromate 

SO₄^-2 sulfate 

monovalent polyatomic anions (-1 charge): 

SO₃^-2 sulfite 

S₂O₃^-2thiosulfate 

BrO₄^- perbromate 

CO₃^-2 carbonate 

BrO₃^- bromate 

C₂O₄^-2 oxalate 

BrO₂^- bromite 

O₂^-2 peroxide 

BrO^- hypobromite 

ClO₄^- perchlorate 

tri and tetravalent anions (-3/-4 charge): 

ClO₃^- chlorate 

ClO₂^- chlorite 

BO₃^-3 borate 

ClO^- hypochlorite 

PO₃^-3 phosphite 

IO₄^- periodate 

PO₄^-3 phosphate 

IO₃^-iodate 

AsO₄^-3 arsenate 

IO₂^-iodite 

AsO₃^-3 arsenite 

IO^- hypoiodite 

MnO₄^- permanganate 

polyatomic anions containing hydrogen: 

MnO₃^- manganate 

HCO₃^- hydrogen carbonate (aka bicarbonate) 

NO₃^- nitrate 

HSO₄^- hydrogen sulfate (aka bisulfate) 

NO₂^- nitrite 

HSO₃^- hydrogen sulfite (aka bisulfite) 

C₂H₃O₂^- acetate 

HPO₄^-2 hydrogen phosphate 

CH₃COO^- acetate 

H₂PO₄^- dihydrogen phosphate 

CN^- cyanide 

HS^- hydrogen sulfide

OCN^- cyanate 

SCN^-thiocyanate 

OH^- hydroxide 

N₃^- azide 

NH₂^- amide 

O₂^- superoxide