VB Description Ionic Structures Hybridization

This object is traditionally achieved in VB theory by taking into consideration ionic VB structures in which the electrons are redistributed amongst the valence orbitals, some of these now being doubly occupied. The simplest example is, of course, the H2 molecule, where one adds to the Heitler-London covalent function 

The Weinbaum and Coulson-Fischer functions, though formally identical, have provided the prototypes for two somewhat divergent developments in 

We continue to ignore the core electrons and consider N valence electrons distributed amongst the valence orbitals in configurations of the form 

The total number of structures with this resultant spin is just31 

It is necessary to form from this large number of functions 

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