An oxidation-reduction (redox) reaction is a chemical reaction in which electrons are transferred between substances.
It involves two simultaneous processes:
- Oxidation – a substance loses electrons, which increases its oxidation state.
- Reduction – a substance gains electrons, which decreases its oxidation state.
In simple terms, one substance gives electrons and another takes them.
Key points:
- Redox reactions always occur together; you cannot have oxidation without reduction.
- The substance that loses electrons is called the reducing agent because it causes another substance to be reduced.
- The substance that gains electrons is called the oxidizing agent because it causes another substance to be oxidized.
Examples include rusting of iron, combustion of fuels, and reactions in batteries.
Redox reactions are central to energy production, metabolism, and industrial processes.