Oxidation: definition in chemistry
Oxidation: Loss of electrons by a substance during a reaction, which increases its oxidation number. It can also mean gain of oxygen or loss of hydrogen.
Oxidation never happens alone: the electrons lost by one substance are gained by another, which is reduced, so the overall reaction is called a redox reaction. The memory aid OIL RIG stands for Oxidation Is Loss, Reduction Is Gain of electrons. Burning, rusting, respiration and the reactions inside batteries are all redox reactions.
Examples
- Rusting — iron atoms lose electrons to become iron ions
- Magnesium burning: 2Mg + O₂ → 2MgO
- Sodium losing an electron: Na → Na⁺ + e⁻
- Ethanol being oxidized to acetic acid as wine turns to vinegar
On the periodic table
Metals on the left of the table, especially the alkali metals in group 1, are oxidized most easily because they lose their few valence electrons readily.