THE DIPOLE MOMENT OF A LONE ELECTRON PAIR

The electronic lone pairs play an important role in intermolecular interactions. In particular, a lone pair protruding in space towards its partner has a large dipole moment, which may interact electrostatically with its partner s multipole moments (see Appendix X, p. 1038). Let us see how the dipole moment depends on the atom to which it belongs and on the type of hybridization. 

Suppose the electronic lone pair is described by the normalized hybrid 

The dipole moment of a single electron described by h is calculated as N = )  

The first two integrals equal zero, because the integrand represents an odd function with respect to the reflection in the plane a = 0. As a result 

We will limit ourselves to A 0, which means we are considering hybrids pro-truding to the right-hand side as in Fig. T.l, and since (2s x 2px) 0, then 0. The negative sign stresses the fact that a negative electron is displaced to the right-hand side (positive x). 

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