Hexavalent

Valence versus oxidation state

In some molecules, there is a difference between valence and oxidation state for a given atom. For example, in disulfur decafluoride molecule S₂F₁₀, each sulfur atom has 6 valence bonds (5 single bonds with fluorine atoms and 1 single bond with the other sulfur atom). Thus, each sulfur atom is hexavalent or has valence 6, but has oxidation state +5. In the dioxygen molecule O₂, each oxygen atom has 2 valence bonds and so is divalent (valence 2), but has oxidation state 0. In acetyleneH−C≡C−H, each carbon atom has 4 valence bonds (1 single bond with hydrogen atom and a triple bond with the other carbon atom). Each carbon atom is tetravalent (valence 4), but has oxidation state −1.