* Oxidation is the loss of electrons.
* Reduction is the gain of electrons.
In the reaction:
2Na(s) + Cl₂(g) → 2NaCl(s)
* Sodium (Na) starts as a neutral atom with one valence electron.
* Chlorine (Cl) starts as a diatomic molecule with seven valence electrons per atom.
* Sodium loses its valence electron to become a positively charged ion (Na+).
* Chlorine gains an electron to become a negatively charged ion (Cl-).
Since sodium loses an electron, it undergoes oxidation. Chlorine gains an electron, so it undergoes reduction.
