Copper and oxygen react to form copper oxide. This is a chemical reaction that involves the transfer of electrons.

There are actually two main types of copper oxide:

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

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

The type of copper oxide formed depends on the conditions of the reaction, such as temperature and the amount of oxygen present.