Compare with reducing agent .An oxidizing agent is a substance that oxidizes another substance by removing electrons from it. Oxidizing agents cause other substances to be oxidized in chemical reactions while they themselves are reduced. For example, nitrate ion is an oxidizing agent in the following reaction:
Cu(s) + 4 H + (aq) + 2 NO 3 - (aq) Cu 2 +(aq) + 2 H 2 O( ) + 2 NO 2 (g)
Copper gets oxidized (its oxidation number goes from 0 to +2) while the nitrogen gets reduced (from +5 in nitrate to +4 in nitrogen dioxide).