Geometry of Molecules Having Single Bonds

Although the molecular orbital description of bonding has some mathematical advantages, simple valence bond representations of structures are adequate for many purposes. The structures of molecules that have only single bonds (and in some cases unshared pairs of electrons on the 

In structures where there is sp, sp2, sp3, or sp3d2 hybridization, all of the positions are equivalent. For a molecule such as PF5, it is found that there are 10 electrons around the phosphoms atom, five from the P atom and one from each of five F atoms. The five pairs have minimum repulsion when they are directed toward the comers of a trigonal bipyramid, so the structure can be shown as 

This structure is somewhat unusual in that the two bonds in axial positions are longer than those in the equatorial positions. The hybrid bond type for the trigonal bipyramid is sp3d (or dsp3 in some cases). However, in reality this is a combination of dp (linear) and sp2 (trigonal planar) hybrids so the orbitals used in the axial and equatorial positions are not equivalent, and this is apparent from the bond lengths shown on the preceding structure. 

H20 molecule utilizes sp3 hybrid orbitals, but the molecule is certainly not tetrahedral  

It is an angular or V -shaped molecule. The geometry of a molecule is predicted by the hybrid orbital type only if there are no unshared pairs of electrons. Hybrid orbital type is determined by the number of electron pairs on the central atom, but the molecular geometry is determined by where the atoms are located. 

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