An experimental study in the literature of the bond dissociation enthalpies of group 14/16 compounds in the gas phase showed that the ratio of the average bond dissociation enthalpy of the triatomic molecule (one half of the atomization enthalpy) to the bond dissociation enthalpy of the diatomic molecule (i.e. its atomization or dissociation enthalpy) is very nearly a constant, ca. 0.8. The current study corroborates these findings by additional thermochemical data from the literature, G2 and G2(MP2) post-Hartree-Fock level quantum chemical calculations and qualitative theoretical reasoning as to the plausibility of the suggested value.