PEAZIT Aha card
Go straight to resources ↓Redox: who loses electrons and who gains them?
Oxidation loses electrons and raises oxidation number. Reduction gains electrons and lowers it. Electrons released by one half-reaction must be accepted by the other.
| Observation | What it means |
|---|---|
| Zn → Zn²⁺ + 2e⁻ | oxidation |
| Cu²⁺ + 2e⁻ → Cu | reduction |
One worked example
- Zn: 0 → +2Oxidation number increases.
- Cu: +2 → 0Oxidation number decreases.
- Zn + Cu²⁺ → Zn²⁺ + CuThe two transferred electrons cancel.
Watch out: A redox reaction need not contain oxygen. Oxidation number is bookkeeping, not always actual atomic charge.
Goal, prerequisites and card origin
What you will learn: Identify oxidation and reduction from electrons.
What you need first: Ion charge.
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Reference for the underlying principle ↗Show connections
Oxidation loses electrons and raises oxidation number. Reduction gains electrons and lowers it. Electrons released by one half-reaction must be accepted by the other.