ADJACENT DIM ISOELECTRONIC MOLECULES AND CHEMICAL SIMILARITY AMONG TRIATOMICS

Isoelectronic molecules and isovalent molecules commonly have chemical similarity. This paper adds a third distribution of molecules and dem onstrates that it exhibits chemical similarity in the case of linear/b ent triatomics: the similarities of same-period triatomics which have equal C-1 + 2C(2) + C-3 = g(C), where C-i is the number of valence ele ctrons of atom i and where i = 2 is the middle atom. It is shown, by g raphical and statistical analyses of critically analyzed data for seve ral observables of main-group molecules, that molecules with constant g(C) are at least as similar as isoelectronic molecules and are vastly more similar than are molecules chosen at random. It is suggested tha t since g(C) can be written additively as (C-1 + C-2) + (C-2 + C-3), a theoretical basis for the new tool might be constructed using a ''dia tomics-in-molecules'' (DIM) or similar theory in which the 1-3 bond is ignored. The generalization to molecules with more than three atoms i s presented.