Molecular Shape, Shape of the Geometrically Active Atomic States, and Hybridization

摘要

In a recent publication [C. A. Nicolaides and Y. Komninos, Int. J. Quant. Chem. 67, 321 (1998)], we proposed that in certain classes of molecules the fundamental reason for the formation of covalent polyatomic molecules in their normal shape is to be found in the existence of a geometrically active atomic state (GAAS) of the central atom, whose shape, together with its maximum spin-and-space coupling to the ligands, predetermines the normal molecular shape (NMS). The shape of any atomic state was defined as that which is deduced from the maxima of the probability distribution #rho#(cos #theta#_(12)) of the angle formed by the position vectors of two electrons of an N-electron atom. Because the shape of the GAAS determines the NMS and because the NMS allows the construction of corresponding hybrid orbitals, we examined and discovered the connection between the GAAS shape and Pauling's function for the strength of two equivalent orthogonal orbitals at angle #theta#_(12) with one another. It is shown that the computed #rho#(cos #theta#_(12)) of the GAAS can be cast in a form which allows the deduction of the composition of the hybrid orbitals of maximum spin states with configurations sp~3, sp~3d~5, sp~3d~5f~7, sl~n, s~2l~n and the demonstration of the central atom's tendency to form bonds in directions which coincide with the nodal cones of the hybrid bond orbitals. These results not only reinforce the validity of the theory as to the fundamental "mechanism" for the formation in the normal shape of coordination compounds and covalently bonded polyatomic molecules, but also provide the justification for the relevance and importance of the hybridization model.