Triatomic molecule

Triatomic molecules are molecules composed of three atoms, of either the same or different chemical elements. Examples include H2O, CO2 (pictured) and HCN. Triatomic molecules are molecules composed of three atoms, of either the same or different chemical elements. Examples include H2O, CO2 (pictured) and HCN. The vibrational modes of a triatomic molecule can be determined in specific cases.