Bond strength and direction

So far, the energetic aspects of covalent bonds have been considered by using molecular orbital theory. Molecular orbital theory is equally well able to give exact information about the geometry of molecules. However, a more intuitive understanding of the geometry of covalent bonds can be obtained via an approach called valence bond theory. (Note that both molecular orbital theory and valence bond theory are formally similar from a quantum mechanical point of view, and either leads to the same result.) 

Valence bond theory starts with the idea that a covalent bond consists of a pair of electrons shared between the bound atoms. Two resulting ideas make it easy to picture covalent bonds. The first of these is the concept that that the direction of a bond will be such as to make the orbitals of the bonding electrons 

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