The Pyramidality of AX3 Molecules

The treatment of eight valence electron AX3 molecules and the effect of the nature of A and X on the degree of pyramidality of these molecules, Le. the effect on the XAX bond angle, proceeds along the same lines as the treatment of the angle problem in eight valence electron AX2 systems. 

Finally, the change in the HXH angle as the electron occupancy of the HOMO is decreased is illustrated by the examples in Table 31. As before, our predictions agree with the available experimental data. 

Certain features of geminal interactions in AX3 molecules need emphasis  

The analysis of the effect of A and X upon the pyramidality of six valence electron AX3 molecules is similar, in principle, to that offered for the previous systems. 

The ideas discussed above have very general applicability. For example, they can be utilized in order to predict the shape of AYX3 molecules as a function of A, Y and X, the shape of planar AXYZ systems as a function of X,Y,Z, etc. In the space below we restrict our attention to only one further example of the applicability of the concept of geminal interactions to problems of molecular stmcture. 

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