Question

arrange group 17 elements in the order of increasing bond dissociation enthalpy ........... explain....

Answer 1

Bond dissociation energy usually decreases on moving down a group as the atomic size increases. However, the bond dissociation energy of F2 is lower than that of Cl2 and Br2. This is due to the small atomic size of fluorine. Thus, the increasing order for bond dissociation energy among halogens is as follows:

I2< F2< Br2< Cl2

Answer 2

Answer:Cl2>Br2>F2>I2

Explanation:

This is an exceptional thing .Bond energy is indirectly proportional to (extent of lone pair -lone pair repulsion between the adjacent atoms).In case of fluorine :

1.bond length is small

2.so,strongest lp-lp repulsion takes place.So,bond dissociation energy is less.

Incase of I2

1.Bond length is much higher thanF2

2.weak repulsion

That's why F2>I2.

Moreover due to strongest lp-lp repulsion (extent of overlapping) F2 is strongest oxidising agent among halogens.