Point negative charges

FIGURE 16.24 In the crystal field theory of complexes, the lone pairs of electrons that serve as the Lewis base sites on the ligands (a) are treated as equivalent to point negative charges (b). 

We are concerned with what happens to the (spectral) d electrons of a transition-metal ion surrounded by a group of ligands which, in the crystal-field model, may be represented by point negative charges. The results depend upon the number and spatial arrangements of these charges. For the moment, and because of the very common occurrence of octahedral coordination, we focus exclusively upon an octahedral array of point charges. 

In an octahedral coordination site, the electrostatic field produced by the six ligands (represented as point negative charges and interacting with an electron in the vicinity of the central cation) is expressed by the potential... 

Accounts for the optical and magnetic properties of complexes —> Ligands are considered to be point negative charges. 

Both the /2g and eg orbitals are raised in energy, but the Cg orbitals are raised more than the orbitals because they are closer to the point negative charges. 

The above results have been derived on the assumption that ionic ligands, such as F, Cl or CN, may be represented by point negative charges. Ligands that are neutral, however, are dipolar (e.g., 20-1 and 20-11), and they... 

In crystal-field theory, ligands are modeled as if they are point negative charges. What is the basis of this assumption, and how does it relate to the nature of metal ligand bonds ... 

Sketch two sets of x- and y-axes with point negative charges equidistant from the origin along the x- and y-axes. On one set of axes, sketch a orbital. On the other, sketch a d 2 orbital. Use your sketches to explain... 

The model described here to account for colours of transition metal ions is a simplified version of crystal field theory. The theory is based on the idea that the bonding in complex ions is purely electrostatic and that the ligands behave as point negative charges. The most common type of complex ion is octahedral, where six ligands form an octahedron around the metal ion. 

Fig. 9.51 An electron at a distance rfrom the nucleus experiences a Coulombic repulsion from all the electrons within a sphere of radius rthat is equivalent to a point negative charge located on the nucleus. The effect of the point charge is to reduce the apparent nuclear charge of the nucleus from Ze to Z e.

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