定义Definition
氧化剂是在氧化还原反应中得到电子、使其他物质被氧化而自身被还原的物质。反应中氧化剂所含某元素的氧化态降低。
An oxidising agent is a substance that gains electrons in a redox reaction, oxidising another substance while itself being reduced. The oxidation state of an element in the oxidising agent decreases.
判断Identifying it
在 Zn + Cu²⁺ → Zn²⁺ + Cu 中，Cu²⁺ 得到电子，氧化态由 +2 降为 0，是氧化剂；Zn 失去电子，是还原剂。可用“失电子是氧化，得电子是还原”（OIL RIG）记忆。氧化剂被还原后的产物称为还原产物。
In Zn + Cu²⁺ → Zn²⁺ + Cu, Cu²⁺ gains electrons and falls from +2 to 0, so it is the oxidising agent; Zn loses electrons and is the reducing agent. The mnemonic OIL RIG says oxidation is loss and reduction is gain of electrons. What the oxidising agent becomes is the reduction product.
常见氧化剂Common oxidising agents
活泼非金属单质：O₂、F₂、Cl₂、Br₂。含高价元素的物质：KMnO₄（酸性，MnO₄⁻ → Mn²⁺）、K₂Cr₂O₇（酸性，Cr₂O₇²⁻ → Cr³⁺）、HNO₃、浓 H₂SO₄、Fe³⁺。过氧化物：H₂O₂、Na₂O₂。
Reactive non-metals: O₂, F₂, Cl₂, Br₂. Compounds with elements in high oxidation states: acidified KMnO₄ (MnO₄⁻ → Mn²⁺), acidified K₂Cr₂O₇ (Cr₂O₇²⁻ → Cr³⁺), HNO₃, concentrated H₂SO₄, Fe³⁺. Peroxides: H₂O₂, Na₂O₂.
氧化性强弱Strength
标准电极电势 E° 越正，电对中的氧化型越容易得电子，氧化性越强：F₂（+2.87 V）> MnO₄⁻/Mn²⁺（+1.51 V）> Cl₂（+1.36 V）> Br₂（+1.07 V）> Fe³⁺/Fe²⁺（+0.77 V）> I₂（+0.54 V）。较强的氧化剂可以把较弱氧化剂的还原型氧化，如 Cl₂ + 2Br⁻ → 2Cl⁻ + Br₂。
The more positive the standard electrode potential E°, the more readily the oxidised form gains electrons and the stronger it is as an oxidising agent: F₂ (+2.87 V) > MnO₄⁻/Mn²⁺ (+1.51 V) > Cl₂ (+1.36 V) > Br₂ (+1.07 V) > Fe³⁺/Fe²⁺ (+0.77 V) > I₂ (+0.54 V). A stronger oxidising agent oxidises the reduced form of a weaker one, e.g. Cl₂ + 2Br⁻ → 2Cl⁻ + Br₂.
年表Timeline
- 1777
拉瓦锡用氧解释燃烧，“氧化”最初指与氧结合
Lavoisier explains combustion with oxygen; oxidation first meant combination with oxygen
- 20世纪初
电子理论建立后，氧化还原被重新定义为电子的转移
With the electron theory, oxidation and reduction are redefined as electron transfer