Divalent

In chemistry, a divalent (sometimes bivalent) element, ion, functional group or molecule has a valence of two. Valency is the number of chemical bonds formed, which may be covalent, polar covalent or ionic.

Examples:

• Divalent elements include calcium and sulfur. While the bonds formed by calcium are ionic; sulfur can form covalent bonds as in H₂S or ionic bonds as in Na₂S.
• Divalent anions have a charge of −2, for example S²⁻ and SO₄²⁻.
• Divalent cations have a charge of +2, for example Fe²⁺, Ca²⁺ and Hg₂²⁺.
• Divalent functional groups include the imino (=NH) and carbonyl (=O).

Water Hardness

Main article: Water hardness

The divalent cations Ca²⁺ and Mg²⁺ contribute to the properties of water that cause it to be hard, such as the formation of limescale.

See also

• Valency (chemistry)
• Valence electron