Question

Bond order of Benzene is 1.5 Explain how.

Answer 1

Hint: To answer this question, we must recall the concept of bond orders. They indicate the type and strength of covalent bonds present in between atoms.

Complete step by step answer:
We can define bond order as the number of bonding pairs of electrons present between two atoms. In a covalent bond between two atoms, a single bond has a bond order of one, double bonds have a bond order of two and triple bonds have a bond order of three.
To determine the bond order of any molecule we should follow the steps mentioned below:
We should first draw the Lewis structure of the molecule.
We should count the total number of bonds and the number of bond groups between individual atoms.
We should then divide the number of bonds between atoms by the total number of bond groups between atoms.
In the case of Benzene, the bond order of a bond is calculated by half the difference between the number of bonding and anti bonding electrons.
\[Bond\,Order = \dfrac{1}{2}(B - A)\]
Each C-C sigma bond is a localized bond. It has 2 bonding electrons and 0 nonbonding electrons.
\[Bond\,Order = \dfrac{1}{2}(2 - 0) = 1\]
Benzene also has 6 pi bonds of which, three are bonding and three are anti bonding.
\[Bond\,Order = \dfrac{1}{2}(6 - 0) = 3\]
\[For\,1\,\pi \,bond = \dfrac{3}{6} = 1.5\]
Hence, the total bond order = 1 + 0.5 = 1.5

Note:
The significance of bond order is that a high bond order indicates more attraction between electrons which means that the atoms are held together more tightly and hence high stability.