When copper reacts with oxygen, it forms copper oxide.

There are two common copper oxides:

* Copper(I) oxide (Cu₂O), also known as cuprous oxide, is a reddish-brown solid.

* Copper(II) oxide (CuO), also known as cupric oxide, is a black solid.

The specific oxide formed depends on the conditions of the reaction, such as temperature and oxygen concentration.

Here's a simplified representation of the reaction:

* Copper + Oxygen → Copper Oxide

For example:

* 2 Cu + O₂ → 2 CuO (formation of copper(II) oxide)

* 4 Cu + O₂ → 2 Cu₂O (formation of copper(I) oxide)