Answer:
The oxidation reaction: Ni → Ni⁴⁺ + 4e.
The reduction reaction: 2Cl₂ + 4e → 4Cl⁻.
Explanation:
The oxidation reaction: in it Ni losses 4 electrons and is oxidized to Ni⁴⁺ according to the reaction:
Ni → Ni⁴⁺ + 4e.
The reduction reaction: every molecule of Cl₂ will gain 2 electrons and is reduced to 2Cl⁻ according to the reaction:
2Cl₂ + 4e → 4Cl⁻.
Ni + 2Cl₂ → NiCl₄.