ELECTRON-PAIR DISTRIBUTIONS AND CHEMICAL BONDING

The electron-pair (intracule and extracule) densities of the first-row hydrides may be understood on the basis of the different chemical-bon ding schemes in this series. Thus, the LiH pair densities show a stron gly ionic nature and may be fairly well described by Li+H-. The CH-pai r densities, on the other hand, may be approximated by the promolecula r superposition of a carbon and a hydrogen atom with an accumulation o f pair density in the internuclear region signifying covalency. In the case of FH, its pair densities show a predominately ionic structure a nd are closer to those of F- than to those of the promolecular superpo sition of a fluorine and a hydrogen atom. The slight deformation of lo ngitudinal pair densities observed in FH is largely due to the presenc e of the H+. (C) 1994 John Wiley & Sons, Inc.