Chemistry

Common Polyatomic Ions

acetate	CH₃COO^-
aluminate	AlO₂^-, Al₂O₄^2-
ammonium	NH₄⁺
arsenate	AsO₄^3-
arsenite	AsO₃^3-
azide	N₃^-
bicarbonate (hydrogen carbonate)	HCO₃^-
tetraborate	B₄O₇^2-
bromate	BrO₃^-
bromite	BrO₂^-
carbide	C₂^2-
carbonate	CO₃^2-
chlorate	ClO₃^-
chlorite	ClO₂^-
chromate	CrO₄^2-
chromite	CrO₂^-
cyanate	NCO^-
cyanide	CN^-
dichromate	Cr₂O₇^2-
dihydrogen phosphate	H₂PO₄^-
dihydrogen phosphite	H₂PO₃^-
disulfide	S₂^2-
formate (formiate)	HCO₂^-
fulminate	CNO^-
hydrogen carbonate (bicarbonate)	HCO₃^-
hydrogen phosphate	HPO₄^2-
hydrogen phosphite	HPO₃^2-
hydrogen sulfate	HSO₄^-
hydrogen sulfite	HSO₃^-
hydronium	H₃O⁺
hydroxide	OH^-
hypobromite	BrO^-
hypochlorite	ClO^-
hypoiodite	IO^-
hypophosphite	PO₂^3-
iodate	IO₃^-
iodite	IO₂^-
mercury(I)	Hg₂²⁺
molybdate	MoO₄^2-
nitrate	NO₃^-
nitrite	NO₂^-
oxalate	(COO)₂^2-
ozonide	O₃^-
perbromate	BrO₄^-
perchlorate	ClO₄^-
periodate	IO₄^-
permanganate	MnO₄^-
peroxide	O₂^2-
phosphate	PO₄^3-
phosphite	PO₃^3-
pyridinium	C₅H₅NH⁺
pyrophosphate	P₂O₇^4-
quaternary ammonium	NR₄⁺
silicate	Si_xO_y
sulfate	SO₄^2-
sulfide	S^2-
sulfite	SO₃^2-
sulfonium	R₃S⁺
superoxide	O₂^-
tartrate	(CH(OH)COO)₂^2-
thiocyanate	CNS^-
thiosulfate	S₂O₃^2-
tosylate (toluenesulfonate)	CH₃C₆H₄SO₃^-
triflate (trifluoromethanesulfonate)	CF₃SO₃^-
tungstate	WO₄^2-

This table is reprinted with some minor editing from the one I found here:

Sources: