Write a balanced half-reaction describing the oxidation of aqueous vanadium (i) cations to aqueous vanadium (v) cations.

The balanced half-reaction: V ⁺ (aq) → V⁵⁺ (aq) + 4e⁻.

Vanadium (I) cations lose four electrons and became vanadium (V) cations.

Oxidation reaction is increasing of oxidation number of element, because element or ion lost electrons in chemical reaction.

Reduction is lowering oxidation number because element or ions gain electrons.