Lexikon
an oxidizer or an oxidizing agent, also called oxidant, can be defined asa chemical compound that readily transfers oxygen atoms, or a substance that gains electrons in a redox chemical reaction. In both cases, the oxidizing agent becomes reduced in the process.
The dangerous substance definition of an oxidizer is a substance that is not necessarily combustible, but may, generally by yielding oxygen, cause or contribute to the combustion of other material. By this definition some materials that are classified as oxidizing agents by analytical chemists or biochemists are not classified as oxidizing agents in a dangerous materials sense.
Oxidising, literally, means converting to oxide. This process can apply to metals (iron converts to iron oxide), nonmetals (sulfur converts to sulfur oxide), and organic matter (mainly carbon and hydrogen converts to carbon oxide and hydrogen oxide). An obvious oxidizer is oxygen, which forms about 21% of air.
Later, the use of the term expanded to include any time where formal charge is increased (losing electrons), and applies to substances which contain no oxygen (typically halogens and substances rich in these elements, and less commonly sulfur). Oxidising is the opposite of reduction, where formal charge is decreased (gaining electrons). Redox reactions occur when oxidation states of the reactants change. In a redox-system the oxidizing agent is reduced, the reducing agent is oxidized. All atoms in a molecule can be assigned an oxidation number. This number changes when an oxidant acts on a substrate.
Many common oxidizers contain oxygen (KClO4 is KCl "plus" 2 O2) and can be considered compact storage of oxygen; a given volume of potassium perchlorate contains much more oxygen than the same volume of air.The most common oxidizers are the following:
Ammonium cerium(IV) nitrate and probably related cerium(IV) compounds
Chlorite, chlorate, perchlorate, and other analogous halogen compounds
Hexavalent chromium compounds such as chromic and dichromic acids and chromium trioxide, pyridinium chlorochromate (PCC), and chromate/dichromate compounds
Hypochlorite and other hypohalite compounds such as bleach
Iodine and other halogens
Nitric acid
Nitrous oxide (N2O)
Osmium tetroxide (OsO4)
Ozone
Permanganate salts
Peroxide compounds
Persulfuric acid
Potassium nitrate (KNO3)
Sulfoxides
Sulfuric acid
Tollens' reagent: ammoniacal silver nitrate
Source: http://en.wikipedia.org/wiki/Oxidizing_agent