Relationships between Electron Density and Bond Order

Relationships between Electron Density and Bond Order 

We would expect there to be a relationship between the electron density among nuclei and the bond length. There is a correlation between bond length and bond order. Bonds get shorter as bond order increases. Pauling defined an empirical relationship for bond order in terms of bond length for C-C, C=C, and C=C bond lengths. For carbon, the parameter a is 0.3  

The concept of a bond order or bond index can be particularly useful in the description of transition structures, where bonds are being broken and formed and the bond order can provide a measure of the extent of reaction at different bonds. It has been suggested that the parameter in the Pauling relationship (1.26) should be 0.6 for bond orders 

MO calculations can define bond order in terms of atomic populations. Mayer developed a relationship for the bond order that is related to the Mulliken population 

Wiberg applied a similar expression to CNDO calculations, where S = 1, to give the bond index, 

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