Write a balanced half-reaction describing the reduction of aqueous chromium (IV) cations to solid chromium.

The balanced half-reaction: Cr⁴⁺ (aq) + 4e⁻ → Cr (s).

Chromium (IV) cations gain four electrons and became solid chromium with neutral charge.

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

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