Heating phosphorus with oxygen gas forms phosphorus oxides. The specific oxide formed depends on the conditions of the reaction, primarily the amount of oxygen present.

Here are the two most common oxides:

* Phosphorus(III) oxide (P₄O₆): Formed when phosphorus is heated in a limited supply of oxygen. It is a white, waxy solid with a pungent odor.

* Phosphorus(V) oxide (P₄O₁₀): Formed when phosphorus is heated in an excess of oxygen. It is a white, crystalline solid that is highly reactive with water.

The reaction with oxygen is highly exothermic, meaning it releases a lot of heat and can be quite dangerous.