Table of Polyatomic Ions

There are a number of ions that are not individual atoms but are composed of multiple atoms that are covalently bonded together. However, this group of atoms is most stable when it has either lost of gained an electron and thus existed as a charged ion. These polyatomic ions are extremely common in chemistry and thus it is important to be able to both recognize and name them. While there are many such ions in the world, you are responsible for knowing the ions listed in the following tables.


NameFormula
ammonium NH4+
nitrite NO2
nitrate NO3
sulfite SO32−
sulfate SO42−
hydrogen sulfate
(aka: bisulfate)
HSO4
thiosulfate S2O32−
oxalate C2O42−
hydroxide OH
NameFormula
phosphite PO33−
phosphate PO43−
hydrogen phosphate HPO42−
dihydrogen phosphate H2PO4
perchlorate ClO4
chlorate ClO3
chlorite ClO2
hypochlorite ClO
bromate BrO3
iodate IO3
NameFormula
acetate
acetate
CH3COO
C2H3O2
carbonate CO32−
hydrogen carbonate
(aka: bicarbonate)
HCO3
chromate CrO42−
dichromate Cr2O72−
permanganate MnO4
peroxide O22−
cyanide CN
cyanate OCN
thiocyanate SCN

Some Metallic Cations

IUPAC Nameolder nameFormula
copper(I)cuprous Cu+
copper(II)cupric Cu2+
iron(II)ferrous Fe2+
iron(III)ferric Fe3+
lead(II)plumbous Pb2+
lead(IV)plumbic Pb4+
mercury(I)mercurous Hg22+
mercury(II)mercuric Hg2+
tin(II)stannous Sn2+
tin(IV)stannic Sn4+