VSEPR model Ligand close-packing

Before discussing the AIM theory, we describe in Chapters 4 and 5 two simple models, the valence shell electron pair (VSEPR) model and the ligand close-packing (LCP) model of molecular geometry. These models are based on a simple qualitative picture of the electron distribution in a molecule, particularly as it influenced by the Pauli principle. 

Gillespie, R.J. (2000). Improving our understanding of molecular geometry and the VSEPR model through the ligand close-packing model and the analysis of electron density distributions. 

XI. THE LIGAND CLOSE-PACKING (LCP) MODEL AND THE VSEPR MODEL... 

R.J. Gillespie and E.A. Robinson (2005) Chemical Society Reviews, vol. 34, p. 396 - A tutorial review Models of molecular geometry that considers the VSEPR model and the more recently developed ligand close-packing (LCP) model. 

For AX molecules with no lone pairs in the valence shell of A, both the VSEPR model and the LCP model predict the same geometries, namely AX2 linear, AX3 equilateral triangular, AX4 tetrahedral, AX5 trigonal bipyramidal, and AX octahedral. Indeed Bent s tangent sphere model can be used equally as a model of the packing of spherical electron pair domains and as a model of the close packing of spherical ligands around the core of the central atom. 

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