# What is meant by a diatomic molecule?

Most of the elemental gases are diatomic (or bimolecular) in their standard states: ${H}_{2} , {O}_{2} , {N}_{2} , {F}_{2} , C {l}_{2}$ etc. The exceptions are the Noble Gases. All of the halogen elements are bimolecular, i.e. ${X}_{2}$, but here only 2 (which?) are gaseous.