The electrostatic model and non-bonding electron pairs

A question which then arises naturally is why are the rules successful This can be answered (following the approach of a recent review [8]) by examination of the angular variation of electrostatic potential about the appropriate atom in an acceptor molecule B in B---HF. The reason for this approach is evident from the fact that the electric charge distribution of the HF molecule 

The few representative examples of n-pair acceptors discussed above (H 2O, H 2 S, H 2CO and SO2) make it clear that the variation of the electrostatic potential at a fixed r with the angle or 0 is a good semi-quantitative method of establishing the existence of and directionality of non-bonding electron pairs in acceptor molecules B. 

Finally, a similar approach is possible for 71-bonding acceptors such as acetylene and ethylene. Appropriate graphs of V 9) versus 6 show a single minimum at the expected angle 6 = 90°. 

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