Answer:
Mg --> Mg²⁺ + 2e
Step-by-step explanation:
Redox reactions consists of both reduction and oxidation reactions.
one species gets oxidised and other species gets reduced, both reactions happen simultaneously giving rise to a redox reaction.
Oxidation reactions could be either loss of electrons or gain of oxygen.
in oxidation the oxidation number of the species will increase
reduction on the other hand is either gain of electrons or gain of hydrogen.
in reduction the oxidation number of the species will reduce
in this reaction the oxidation half reaction is
Mg --> Mg²⁺ + 2e
Mg is losing electrons therefore its being oxidised