Compare with binary compound and polyatomic molecule. A molecule that contains only two atoms. All of the noninert gases occur as diatomic molecules; e. g. hydrogen, oxygen, nitrogen, fluorine, and chlorine are H2, O2, N2, F2, and Cl2, respectively.

a molecule composed of two atoms.

a molecule comprising two atoms

A molecule containing only two atoms, such as hydrogen as H2 or oxygen as O2.

Diatomic molecules are molecules formed of two atoms, of the same or different chemical elements. The prefix di- means two in Greek. Diatomic elements are those that almost exclusively exist as diatomic molecules, known as homonuclear diatomic molecules in their natural elemental state when they are not chemically bonded with other elements.