Question

Arrange the following bonds according to their average bond energies in descending order:
$C-Cl,C-Br,C-F,C-I$

JEE MAIN 2020

• A. $C-Cl>C-Br>C-I>C-F$
• B. $C-F>C-Cl>C-Br>C-I$
• C. $C-Br>C-I>C-Cl>C-F$
• D. $C-I>-Br>C-Cl>C-F$

Answer 1

The correct option is B $C-F>C-Cl>C-Br>C-I$

In $C-F$ there is $2p-2p$ overlapping involved, in $C-Cl$ the overlapping involved is $2p-3p$ whereas for $C-Br$ and $C-I$ the overlapping involved are $2p-4p$ and $2p-5p$ respectively. The bond length for the various type of overlapping can be given as;
$2p-2p<2p-3p<2p-4p<2p-5p$

As we know that $\text{Bond energy}\propto \frac{1}{\text{Bond Length}}$

The order of bond energy is:
$C-F>C-Cl>C-Br>C-I$