Question

What is a diatomic molecule?

Answer 1

Diatomic molecules contain two atoms that are chemically bonded. If the two atoms are identical, as in, for example, the oxygen molecule (O2), they compose a homonuclear diatomic molecule, while if the atoms are different, as in the carbon monoxide molecule (CO), they make up a heteronuclear diatomic molecule.
Sources:
https://www.britannica.com/science/molecule#ref257752