The given chemical reaction is:
Mg + Cl₂ → Mg²⁺ + 2Cl⁻
The reaction can be broken down into two half-reactions as follows:
Mg → Mg²⁺ + 2e⁻ ------(1)
Cl₂ + 2e⁻ → 2Cl⁻ ------(2)
Reaction (1) is an oxidation reaction as it involves loss of electrons.
Reaction (2) is reduction reaction as it involves gain of electrons.
The oxidation state of Mg changes from 0 (Mg) to +2 (Mg2+). Hence, Mg is the oxidized substance