SCGVB Theory

Dunning, T. H., Jr.; Woon, D. E.; Xu, L. T.; Takeshita, T. Y.; Lindquist, B. A.; Leiding, J. Recoupled Pair Bonding: Unifying the Theory of Valence for the Main Group Elements. Ann. Rep. Comput. Chem. 2016, 12, 1-33.

The valence of an element often exceeds the number of singly occupied orbitals in the electronic configuration of the ground state of the atom. In the early main group elements, the increase in valence is attributed to the formation of sp n hybrid orbitals and in the late main group elements beyond the first row to the formation of 3-center, 4-electron (3c-4e) bonds. Our studies have shown that a single new conceptdrecoupled pair bondingdunderlies the increases in valence in both groups of elements. In this report, we describe recent studies of the CFn and SFn molecules that illustrate the nature of recoupled pair bonds and recoupled pair bond dyads and compare and contrast the recoupled pair bonds formed with the electrons in ns lone pairs (early main group elements) and np lone pairs (late main group elements beyond the first row). Recoupled pair bonding also accounts for many of the other differences in the chemistry of the elements in the first and subsequent rows of the Periodic Table, which is known as the first row anomaly.

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