Question

Deduce the oxidation number of S in the following species : 

i. SO₂

ii. \(SO_4^{2-}\) 

Answer 1

i. SO₂ is a neutral molecule.

∴ Sum of oxidation numbers of all atoms of SO₂ = 0

∴ (Oxidation number of S) + 2 × (Oxidation number of O) = 0

∴ Oxidation number of S + 2 × (- 2) = 0

∴ Oxidation number of S in SO₂ = 0 – (- 4)

∴ Oxidation number of S in SO₂ = +4

ii. \(SO_4^{2-}\) is an ionic species.

∴ Sum of the oxidation numbers of all atoms of \(SO_4^{2-}\) = – 2

∴ (Oxidation number of S) + 4 × (Oxidation number of O) = – 2

∴ Oxidation number of S in \(SO_4^{2-}\) = – 2 – 4 × (-2) = – 2 + 8

∴ Oxidation number of S in \(SO_4^{2-}\) = +6