which elements occur as a diatomic molecule
If the diatomic molecule consists of atoms from two different elements, then it is a heteronuclear diatomic molecule. There are seven elements that naturally occur as homonuclear diatomic molecules in their gaseous states: hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine. Bromine and iodine need slightly higher temperatures than room temperature to occur as gaseous diatomic molecules.