Redox reaction: definition in chemistry
Redox reaction: A reaction in which electrons are transferred from one substance to another, so that one substance is oxidized and another is reduced.
The name combines reduction and oxidation, which always happen together. The substance that gains electrons is the oxidizing agent, and the one that loses them is the reducing agent. Chemists track redox reactions with oxidation numbers, which go up for the substance oxidized and down for the substance reduced. Batteries, corrosion, combustion, photosynthesis and respiration all depend on redox reactions.
Examples
- Zinc in copper sulfate solution: Zn + Cu²⁺ → Zn²⁺ + Cu
- Sodium burning in chlorine: 2Na + Cl₂ → 2NaCl
- Iron ore reduced in a blast furnace: Fe₂O₃ + 3CO → 2Fe + 3CO₂
- A lithium-ion battery powering a phone
On the periodic table
Reactive metals on the left of the table are strong reducing agents, while reactive nonmetals at the upper right, such as fluorine and oxygen, are strong oxidizing agents.