Electronic charge around atom

Table 23.2 shows the net charge of the center lithium ion and the bond overlap population between the center lithium ion and neighboring halide ions obtained for model II. The net charge values decrease with increasing atomic number of halide ion. On the other hand, the bond overlap population values are almost identical. This is probably due to increased electronic charge around the lithium ion. 

Charge density analyses can provide experimental information on the concentration of electron density around atoms and in intra- and intermolecular bonds, including the location of lone pairs. Transition metal d-orbital populations can be estimated from the asphericity of the charge distribution around such metal centers. A number of physical properties that depend upon the electron density distribution can also be calculated. These include atomic charges, dipole and higher moments, electric field gradients, electrostatic potentials and interaction... 

It is reasonable to speculate that the differences in elemental densities at the MNM transition are related to characteristic atomic properties. One such property, for example, is the radius of the principal maximum in the charge density of the ns valence orbital, a which enters into the Mott criterion (Section 2.3.4). A related property is the static polarizability a of the isolated atom. The polarizability formed the basis of very early discussions of the MNM transition by Goldhammer (1913) and Herzfeld (1927). They pointed out that electrons localized around atomic nuclei constitute polarizable objects and their internal dynamics in dense assemblies leads to local corrections to the polarizing tendency of any external field impressed on the system. For an isotropic material, the correction factor has the form [1 — (4Tr/3)lVa] where N is the number of atoms per unit volume. If a is taken to remain roughly... 

Dispersion forces caimot be explained classically but a semiclassical description is possible. Consider the electronic charge cloud of an atom to be the time average of the motion of its electrons around the nucleus. 

Examine the structure, atomic charges and electrostatic potential map of phenyl diazonium ion. Which atom(s) appears to carry most of the positive charge Is the electron distribution around this atom(s) uniform, or are some regions more electron rich and others more electron poor Draw appropriate resonance contributors. 

Plus (+) and minus (-) signs are often used to indicate the presence of formal charges on atoms in molecules. Assigning formal charges to specific atoms is a bookkeeping technique that makes it possible to keep track of the valence electrons around an atom and offers some clues about chemical reactivity. 

Figure 11.14 Solvation of a carbocation by water. The electron-rich oxygen atoms of solvent molecules orient around the positively charged carbocation and thereby stabilize it.

For a proton, with its +1 charge, to separate from the molecule, the electron density around the oxygen should be as low as possible. This will weaken the O—H bond and favor ionization. The electron density around the oxygen atom is decreased when—... 

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