Why do molecules of oxygen have to have an even number of atoms?

Answer:this is all i found out

Oxygen is known as a diatomic molecule. Oxygen atom has atomic number as 8 so it has its K shell completely filled with 2 electrons. While it has only 6 electrons in L shell which requires 8 electrons to get inert gas configuration. So oxygen atom shares 2 electrons with another oxygen atom to form a diatomic molecule.