MOLECULAR SHAPE, SHAPE OF THE GEOMETRICALLY ACTIVE ATOMIC STATES, ANDHYBRIDIZATION

In a recent publication [C. A. Nicolaides and Y. Komninos, Int. J. Qua nt. Chem. 67, 321 (1998)], we proposed that in certain classes of mole cules the fundamental reason for the formation of covalent polyatomic molecules in their normal shape is to be found in the existence of a g eometrically active atomic stare (GAAS) of the central atom, whose sha pe, together with its maximum spin-and-space coupling to the Ligands, predetermines the normal molecular shape (NMS). The shape of any atomi c state was defined as that which is deduced from the maxima of the pr obability distribution rho(cos theta(12)) of the angle formed by the p osition vectors of two electrons of an N-electron atom. Because the sh ape of the GAAS determines the NMS and because the NMS allows the cons truction of corresponding hybrid orbitals, we examined and discovered the connection between the GAAS shape and Pauling's function for the s trength of two equivalent orthogonal orbitals at angle theta(12) with one another. It is shown that the computed rho(cos theta(12)) of the G AAS can be cast in a form which allows the deduction of the compositio n of the hybrid orbitals of maximum spin states with configurations sp (3), sp(3)d(5), sp(3)d(5)f(7), sl(n), s(2)l(n) and the demonstration o f the central atom's tendency to form bonds in directions which coinci de with the nodal cones of the hybrid bond orbitals. These results not only reinforce the validity of the theory as to the fundamental ''mec hanism'' for the formation in the normal shape of coordination compoun ds and covalently bonded polyatomic molecules, but also provide the ju stification for the relevance and importance of the hybridization mode l. (C) 1999 John Wiley & Sons, Inc.