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Polyatomic ion

A polyatomic ion is an ion consisting of a molecule with covalently bonded atoms or of a metal complex that can be considered as acting as a single unit in the context of acid/base chemistry or in the formation of salts. Note, a polyatomic ion is also referred to in older works as a radical. In current usage the term radical refers to free radicals which are uncharged species with an unpaired electron.

A large polyatomic ion will often be considered as the conjugate acid or conjugate base of a neutral molecule, for example the conjugate acid of adrenaline at the amine group.

Note that many of the common negatively-charged anionic polyatomic ions are conjugate bases of acids derived from the oxides of non-metallic elements. For example the sulfate or SO42- ion is derived from H2SO4 which can be regarded as SO3 + H2O.

Common polyatomic ions

Common polyatomic ions
acetate CH3COO-
aluminate AlO2-, Al2O42-
ammonium NH4+
arsenate AsO43-
arsenite AsO33-
azide N3-
bicarbonate (hydrogen carbonate) HCO3-
tetraborate B4O72-
bromate BrO3-
bromite BrO2-
carbide C22-
carbonate CO32-
chlorate ClO3-
chlorite ClO2-
chromate CrO42-
chromite CrO2-
cyanate CNO-
cyanide CN-
dichromate Cr2O72-
dihydrogen phosphate H2PO4-
dihydrogen phosphite H2PO3-
disulfide S22-
formate (formiate) HCO2-
hydrogen carbonate (bicarbonate) HCO3-
hydrogen phosphate HPO42-
hydrogen phosphite HPO32-
hydrogen sulfate HSO4-
hydrogen sulfite HSO3-
hydronium H3O+
hydroxide OH-
hypobromite BrO-
hypochlorite ClO-
hypoiodite IO-
hypophosphite PO23-
iodate IO3-
iodite IO2-
mercury(I) Hg22+
molybdate MoO42-
nitrate NO3-
nitrite NO2-
oxalate (COO)22-
perbromate BrO4-
perchlorate ClO4-
periodate IO4-
permanganate MnO4-
peroxide O22-
phosphate PO43-
phosphite PO33-
pyridinium C5H5NH+
pyrophosphate P2O74-
quaternary ammonium NR4+
silicate SixOy
sulfate SO42-
sulfide S2-
sulfite SO32-
superoxide O2-
tartrate (CH(OH)COO)22-
thiocyanate CNS-
thiosulfate S2O32-
tosylate (toluenesulfonate) CH3C6H4SO3-
triflate (trifluoromethanesulfonate) CF3SO3-

See also

External links



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01-04-2007 01:21:04