In chemistry, an oxidizing agent (oxidant, oxidizer) is a substance that has the ability to oxidize other substances — in other words, to cause them to lose electrons. Common oxidizing agents are oxygen, hydrogen peroxide and the halogens.
In one sense, an oxidizing agent is a chemical species that undergoes a chemical reaction that removes one or more electrons from another atom. In that sense, it is one component in an oxidation-reduction (redox) reaction. In the second sense, an oxidizing agent is a chemical species that transfers electronegative atoms, usually oxygen, to a substrate. Combustion, many explosives, and organic redox reactions involve atom-transfer reactions.
Common oxidizing agents (O-atom transfer agents)
Oxygen (O2)
Ozone (O3)
Hydrogen peroxide (H2O2) and other inorganic peroxides, Fenton's reagent
Fluorine (F2), chlorine (Cl2), and other halogens
Nitric acid (HNO3) and nitrate compounds
Sulfuric acid (H2SO4)
Peroxydisulfuric acid (H2S2O8)
Peroxymonosulfuric acid (H2SO5)
Chlorite, chlorate, perchlorate, and other analogous halogen compounds
Hypochlorite and other hypohalite compounds, including household bleach (NaClO)
Hexavalent chromium compounds such as chromic and dichromic acids and chromium trioxide, pyridinium chlorochromate (PCC), and chromate/dichromate compounds
Permanganate compounds such as potassium permanganate
Sodium perborate
Nitrous oxide (N2O), Nitrogen dioxide/Dinitrogen tetroxide (NO2 / N2O4)
Potassium nitrate (KNO3), the oxidizer in black powder
Sodium bismuthate