The oxidation number for sulfur in SO2 is +4. To find this oxidation number, it is important to know that the sum of the oxidation numbers of atoms in compounds that are neutral must equal zero. In the compound sulfur dioxide (SO2), the oxidation number of oxygen is -2.
To find the oxidation number of sulfur, it is simply a matter of using the formula SO2 and writing the oxidation numbers as S = (x) and O2 = 2(-2) = -4. Using the rule and adding the oxidation numbers in the compound, the equation becomes x +(-4 ) = 0. Solving for x, it is evident that the oxidation number for sulfur is +4.
In chemical compounds, an atom's oxidation number refers to the charge that atoms have if the compound consists of only ions. When writing compound formulas or reactions, there are rules used to assign oxidation numbers.