Triatomic molecule

4He3, the helium trimer is only weakly bound by van der Waals force and is in an Efimov state.

All triatomic molecules may be classified as possessing either a linear, bent, or cyclic geometry.

[further explanation needed] Linear triatomic molecules owe their geometry to their sp or sp3d hybridised central atoms.

Well-known linear triatomic molecules include carbon dioxide (CO2) and hydrogen cyanide (HCN).

Xenon difluoride (XeF2) is one of the rare examples of a linear triatomic molecule possessing non-bonded pairs of electrons on the central atom.