Oxidation & Reduction in Terms of Oxidation Numbers

Question 1

What happens to an element’s oxidation number when it is oxidised?

Answer 1

When an element is oxidised, its oxidation number increases, i.e. oxidation is an increase in oxidation number.

Question 2

What happens to an element’s oxidation number when it is reduced?

Answer 2

When an element is reduced, its oxidation number decreases, i.e. reduction is a decrease in oxidation number.