An oxidizing agent (oxidant) is a substance that accepts electrons from another species during a redox reaction, thereby causing that other species to be oxidized while the oxidizing agent itself is reduced. Common oxidizing agents include oxygen (O₂), hydrogen peroxide (H₂O₂), potassium permanganate (KMnO₄), and chlorine (Cl₂). Oxidizing agents are critical in combustion, corrosion, bleaching, respiration, and industrial synthesis processes.
| Oxidizing Agent | Formula | Reduced Product | Common Use |
|---|---|---|---|
| Oxygen | O₂ | H₂O or O²⁻ | Combustion, respiration |
| Hydrogen peroxide | H₂O₂ | H₂O | Bleaching, disinfection |
| Potassium permanganate | KMnO₄ | MnO₂ or Mn²⁺ | Organic oxidation, water treatment |
| Chlorine | Cl₂ | Cl⁻ | Water disinfection, bleach production |
| Nitric acid | HNO₃ | NO₂ or NO | Metal dissolution, explosives synthesis |
| Ozone | O₃ | O₂ | Water purification, sterilization |
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The oxidation number (or oxidation state) is a hypothetical charge assigned to an atom in a molecule or ion, assuming all bonds are fully ionic and electrons are transferred to the more electronegative atom. It is a bookkeeping tool used to track electron transfer in redox reactions, with defined rules for elements, ions, and compounds. Oxidation numbers help identify which species is oxidized (loses electrons, oxidation number increases) and which is reduced (gains electrons, oxidation number decreases) in a reaction.
A reducing agent (reductant) is a substance that donates electrons to another species in a redox reaction, causing that species to be reduced while the reducing agent itself is oxidized. Strong reducing agents include hydrogen gas (H₂), carbon (C), metals such as sodium and iron, and compounds like sodium borohydride (NaBH₄). Reducing agents are essential in metallurgy for extracting metals from ores, in organic synthesis, and in biological processes such as the Calvin cycle.
From French "oxydant" (oxidizing), derived from Greek "oxys" (sharp, acid) and Latin "agens" (doing, acting). The term reflects the historical association of oxidation with oxygen, coined around the 18th century by Antoine Lavoisier.