Write a balanced half-reaction describing the oxidation of gaseous dihydrogen to aqueous hydrogen cations.

Explanation:

Oxidation-reduction reaction or redox reaction is defined as the reaction in which oxidation and reduction reactions occur simultaneously.

Oxidation reaction is defined as the reaction in which a substance looses its electrons. The oxidation state of the substance increases.

Reduction reaction is defined as the reaction in which a substance gains electrons. The oxidation state of the substance gets reduced.

On reactant side:

Oxidation state of hydrogen = 0

On product side:

Oxidation state of = +1

The oxidation state of hydrogen increases from 0 to +1. Thus, it is getting oxidized and it undergoes oxidation reaction.

a electronegativity decreases beacuse the size of nucleus is bigger.