Knowledge Bank

“Valence rules for atoms or ions of Groups III through VIII, giving both the correct numbers of e-bonds which can he formed and their geometrical arrangements, can be stated succinctly in terms of the ground state electron configuration of the free atom or ion. Simple diagrams have been involved for the relevant electron configurations $s2p,s2p2,\dots s2p$ to serve as a useful device for recalling these results. The procedure is readily extended to cover $\pi$-bonding but not, in general, rings. These results, together with other $data1$, suggest that the symmetries of the ligand arrangements about these atoms may be determined by their use of only s and p orbitals, with d orbitals at most a secondary role. A tabulation, analogous to that of $Kimball2$, has therefore been of the highest symmetries of ligand arrangements possible for various numbers of liquids, under the assumption that only s and p orbitals of the central atom not occupied by unshared pairs are available for bonding. In the few instances of discrepancy, the lower observed symmetry may well be a consequence of electron pair-pair repulsions, causing the molecule lo become distorted in such a way as to permit mixing of orbitals initially of different symmetries.”