Valence shell charge concentrations

The two bonding maxima and the two nonbonding maxima in the valence shell charge concentration of the sulfur atom in SCF have an approximately tetrahedral atfangement just like the two bonding domains and the two nonbonding domains of the VSEPR model. As we shall see, this correspondence is found for many other molecules, and so it seems reasonable... 

Figure 7.6 Contour maps of L for H2O, (left in the molecular plane right, perpendicular to the molecular plane), NH3 (in a symmetry plane through N and one H), and CH4 (in a symmetry plane through C and two H s). The maxima in the valence shell charge concentration are indicated by the dots.

The localization of the valence shell electrons of the central atom into pairs that is the basis of the VSEPR model can be clearly seen in the contour map of L for a plane through the carbon atom and two Cl ligands for the CC14 molecule given in Figure 8.8. There is a maximum in the valence shell charge concentration of both carbon and chlorine along each... 

The postulates of VSEPR theory are consistent with the partitioning of electron density according to Bader s atoms-in-molecules method [173], in which the electron pairs return as the valence shell charge concentration. 

The outer quantum shell of an atom is divided into an inner region over which < 0 and an outer one over which > 0. The portion of the shell over which V p < 0, is called the valence-shell charge concentration or VSCC. Within this shell is the sphere over whose surface the valence electronic charge is maximally and uniformly concentrated. 

Valence-shell charge concentrations with four maxima... 

The Laplacian thus displays where the electronic charge is locally concentrated or depleted [25, 26]. The topology of the valence shell charge concentration (VSCC), the region of the outer shell of an atom over which V p < 0, is in accordance with the Lewis and valence shell electron pair repulsion model. To each local maximum in the VSCC, a pair of bonded or non-bonded electrons can be assigned (Fig. 2). 

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