Question

What is the oxidation number of sulfur (S) in magnesium sulfate (MgSO4)?

A. +2

B. +3

C. +6 <--?

D. +7

Answer 1

Mg: it has a fixed oxidation number 2+ in any compound

O: it has an oxidation number 2-, except in peroxides.

The oxidation number of S is such that the net charge of the compound, Mg SO4 is zero.

Call x the oxidation number of S:

(2+) + (x) + 4(2-) = 0 => x = +8 - 2 = +6

Answer: Option C. +6