Diatomic

Diatomic molecules are molecules formed of two atoms of the same element. Diatomic elements are those that almost exclusively exist as diatomic molecules in their natural elemental state, not chemically bonded with other elements. Examples include H₂ and O₂. Diatomic elements rarely exist in their atomic form. Earth's atmosphere is comprised almost completely (99%) of diatomic oxygen (O₂) and nitrogen (N₂).

Oxygen also exists as the triatomic molecule ozone (O₃).

The diatomic elements are hydrogen, nitrogen, oxygen, and the halogens: fluorine, chlorine, bromine, iodine, and astatine. (They can be remembered as H.O.N. and the Halogens.) Astatine is so rare in nature, its most stable isotope has a half-life of only 8.1 hours, that it is usually not included. The seven primary diatomic elements (excluding Hydrogen) form a '7' shape on the periodic table, beginning with Nitrogen.

The bonds between the two diatomic atoms are non polar and almost 100% covalently bonded.