Question

Order of reactivity towards halogenation is ${F_2} > C{l_2} > B{r_2} > {I_2}$.
State true or false.
A) True
B) False

Answer 1

Hint: The reactivity of halogens depends highly upon their size and the bond length present between the two atoms of a molecule. The more the value of bond length the less will be the reactivity of that molecule. One can apply these concepts for each halogen molecule and find out the correct order.

Complete step by step answer:
1) First of all let’s see which factors impact the reactivity of a molecule. Each molecule has a size and it contributes to the bond length of a molecule. The more is the size of an atom the more will be its bond length in the molecule.
2) The bond length is inversely proportional to the reactivity of a molecule.
3) The bond energy of a molecule is also inversely proportional to the reactivity of a molecule. The more the bond energy it will take more energy to break the bond resulting in the less reactivity of that molecule.
4) By using the above information we can write the order of bond energy as, ${I_2} > B{r_2} > C{l_2} > {F_2}$.
5) As the reactivity is inversely proportional to the bond energy of a molecule the above order will get reversed as, ${F_2} > C{l_2} > B{r_2} > {I_2}$.
6) Hence, the given statement, order of reactivity towards halogenation is ${F_2} > C{l_2} > B{r_2} > {I_2}$ which is TRUE.


Note:
The inter electronic repulsions present in the small-sized atom of fluorine makes the bond dissociation energy of atom Fluorine lower than the atoms chlorine and bromine. Due to the small size of the atom, there is a high electronic density present. The presence of greater inter electronic repulsion in the fluorine molecule​ makes it highly reactive among all halogens.