Assigning Oxidation Numbers

COMPOUNDS

5.10 - Oxidation Numbers

What is the oxidation number of sulfur in SO₂?

The oxidation number of each oxygen is -2 (Rule #6). There are two oxygen atoms.
The overall charge of the compound is zero, so the sum of the oxidation numbers of all the atoms in the formula is zero (Rule #8).

Let the oxidation number of sulfur be represented as S. Set up the equation and solve for S.

S + 2 (-2) = 0

S = +4

The oxidation number of sulfur in SO₂ is +4.

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