The Saga of Hypervalent Molecules

A CD molecule has one or more vacant orbitals (holes) in the core, an LD molecule has one or more holes in the ligands, and an SD molecule has holes in both 

It is evident that construction of a bond diagram, a direct projector of the R CW, immediately identifies a molecule as one of the eleven possible types defined above. 

Up until this point, we have dealt mostly with CE, CD, C-HERM, and N systems. An example of a CE system is H2O, an example of a CD system is BeH2f an example of a C-HERM system is C2H2, and an example of an N system is CH. We now turn our attention to other types of molecules noting that the term electron excessive , or, hypervalent is used by chemists in order to single out LE and SE molecules and the term electron deficient is used in order to denote CD, LD, and SD molecules. As 

In this way, the detailed MOVB diagram projects very explicitly the lowest energy perfect pairing CW of the system in question. 

In this chapter, we focus our attention primarily on SE molecules. However, 

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