Copper oxide is also known as:

Copper is a metal. As copper is present below hydrogen in the reactivity series, it slowly combines with oxygen to form Copper(II)oxide. This copper(II) oxide is blackish-grey in colour and is also called black oxide.

The chemical equation of formation of copper (II) oxide is given as:

$2{\mathrm{Cu}}_{\left(\mathrm{s}\right)}+{\mathrm{O}}_{2\left(\mathrm{g}\right)}\to 2{\mathrm{CuO}}_{\left(\mathrm{s}\right)}$