Classification of molecules:

Molecules can also be classified as monoatomic or polyatomic

Monoatomic molecules:

A molecule that contains only one atom is called monoatomic.

Examples:

Inert gases consist of monoatomic molecules such as He, Ne, Ar, kr, Rn.

Polyatomic molecules:

Molecules that contain two or more similar or different atoms are called polyatomic molecules.

Examples:

H₂, O₂, HCL, NH₃ etc are polyatomic molecules