What is the oxidation state of an individual sulfur atom in so42−?

The oxidation state of single oxygen atom is -2 since it is more electronegative and like to gain electrons.

The sum of the oxidation states of each atom = charge of compound

Let’s say the oxidation state of Sulfur is x.

Hence,

      x +4 * (-2) = -2

      x – 8         = -2

                  x   = +6

The oxidation state of individual Sulfur atom is +6