Given the balanced equation representing a reaction:

Fe2O3 + 2Al--> Al2O3 + 2Fe

During this reaction, the oxidation number of Fe changes from

(1) + 2 to 0 as electrons are transferred

(2) + 2 to 0 as protons are transferred

(3) + 3 to 0 as electrons are transferred

(4) + 3 to 0 as protons are transferred

Oxidation number of an atom is the charge that atom would have if the compound was composed of ions. Oxidation numbers are positive or negative numbers, but don't confuse them with positive or negative charges on ions or valences.

In this balanced equation, the oxidation number of Fe cation in the reactant is + 3 because the valence electrons of Fe is + 3. In the product formed, the oxidation number of Fe is 0 since it is a metal and according to its rule the oxidation number of an element in its free (uncombined) state is zero.

Therefore, the oxidation number of Fe changes from + 3 to 0 as electrons transferred.