What Is Valence or Valency in Chemistry
Valency
The combining capacity of an element is known as its valency.
Formulae and valencies of common ions
Electropositive Ions | |||
Monovalent | Bivalent | ||
Name | Formula | Name | Formula |
Potassium | K+ | Barium | Ba2+ |
Sodium | Na+ | Calcium | Ca2+ |
| Copper [I] | Cu+ | Magnesium | Mg2+ |
Manganese [II] | Mn2+ | ||
| Zinc | Zn2+ | ||
Silver | Ag+ | Iron [II] | Fe2+ |
Ammonium | NH4+ | ||
Hydrogen | H+ | Nickel | Ni2+ |
Cobalt | Co2+ | ||
Tin [II] | Sn2+ | ||
| Cadmium | Cd2+ | ||
Lead [II] | Pb2+ | ||
| Copper [II] | Cu2+ | ||
Trivalent | Tetravalent | ||
Name | Formula | Name | Formula |
Aluminium | Al3+ | Manganese [II] | Mn4+ |
Chromium | Cr3+ | Tin [IV] | Sn4+ |
Iron [III] | Fe3+ | Lead [IV] | Pb4+ |
Gold | Au3+ | Platinum | Pt4+ |
| Electropositive Ions | |||
| Monovalent | Bivalent | ||
| Name | Formula | Name | Formula |
| Hydroxide | OH– | Carbonate | CO32– |
| Hydride | H– | Chromate | CrO42– |
| Fluoride | F– | Dichromate | Cr2O72– |
| Chloride | Cl– | Manganate | MnO42– |
| Bromide | Br– | Tetrathionate | S4O62– |
| Iodide | I– | Sulphide | S2– |
| Bicarbonate | HCO3– | Sulphite | SO32– |
| Bisulphite | HSO3– | Sulphate | SO42– |
| Bisulphate | HSO4– | Oxide | O2– |
| Chlorate | ClO3– | Zincate | ZnO22– |
| Hypochlorite | ClO– | Thiosulphate | S2O32– |
| Nitrite | NO2– | ||
| Nitrate | NO3– | ||
| Permanganate | MnO4– | ||
| Trivalent | Tetravalent | ||
| Name | Formula | Name | Formula |
| Nitride | N3– | Ferrocyanide | Fe(CN)64– |
| Phosphate | PO43– | ||
| Ferricyanide | Fe(CN)63– | ||
| Phosphide | P3– | Pt4+ | |
Variable valency
There are certain elements that exhibit more than one valencies in their ions (or compounds).
Example: Iron can exist as Fe2+ or Fe3+ in its compounds. In such cases the name of the ion with lower valency ends with a suffix ‘ous’ while that with higher valency ends with a suffix ‘ic’.
Some basic ions exhibiting variable valency
Name of ions | Formula |
Cuprous | Cu+ |
Cupric | Cu2+ |
| Mercurous | Hg22+ |
Mercuric | Hg2+ |
| Ferrous | Fe2+ |
Ferric | Fe3+ |
| Plumbous | Pb2+ |
plumbic | Pb4+ |
| Stannous | Sn2+ |
Stannic | Sn4+ |
| Aurous | Au+ |
| Auric | Au3+ |