Bonding models for tetravalent compounds

The fact that the Group 14 elements form four single bonds is in agreement with the Lewis electron pair model. In these compounds the central atom is surrounded by four bonding electron pairs and the structure is tetrahedral in agreement with the VSEPR model. The observation that the E-Cl bonds in the tetrachlorides are shorter than in the dichlorides is, however, difficult to rationalize in terms of the VSEPR model. 

The first step is to form pure p type orbitals pointing towards the ligands  

These orbitals are normalized if T) = 3. We now form the hybrid orbitals  

These orbitals will have the same shape if all coefficients (a) are equal. Finally we fix the value of a by insisting that the hybrids are orthogonal  

Problem 13.1 Show that equation (13.1) yields = 3. The hybrids are therefore denoted by sp.  

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