Question

Correct order of reactivity of halogens is:
A. ${{\rm{I}}_{\rm{2}}} > {\rm{B}}{{\rm{r}}_2} > {\rm{C}}{{\rm{l}}_2} > {{\rm{F}}_{\rm{2}}}$
B. \[{\rm{B}}{{\rm{r}}_2} > {{\rm{I}}_{\rm{2}}} > {\rm{C}}{{\rm{l}}_2} > {{\rm{F}}_{\rm{2}}}\]
C. \[{\rm{C}}{{\rm{l}}_2} > {\rm{B}}{{\rm{r}}_2} > {{\rm{I}}_{\rm{2}}} > {{\rm{F}}_{\rm{2}}}\]
D. \[{{\rm{F}}_{\rm{2}}} > {\rm{C}}{{\rm{l}}_2} > {\rm{B}}{{\rm{r}}_2} > {{\rm{I}}_{\rm{2}}}\]

Answer 1

Hint: We know that the reactivity of halogens is found to be dependent on their electronegativity. More is the electronegativity; more is the ability of the halogen to show protonation. Thus, more is the reactivity of halogen.

Complete step by step answer:
It is known to us that the $17$ group of periodic tables consist of halogen. Fluorine, chlorine, bromine, and iodine are the members of the halogen family. They exist as diatomic molecules. The general electronic configuration of halogens is ${\rm{n}}{{\rm{s}}^{\rm{2}}}{\rm{n}}{{\rm{p}}^{\rm{5}}}$. They need only one electron in their outermost shell to complete their octet. Therefore, they are highly electronegative in nature. So we can say that they easily undergo reactions with group one and two metals and also show reactions with hydrogen atoms.
We know that, in a periodic table on moving down a group, the atomic radius increases because of which electrons can be lost more quickly. Down the group, when atomic radius increases the attraction that exists between the nucleus and electrons of the outermost shell becomes less, due to an increased distance between them. Also, the electronegativity decreases down the group. Therefore, we can say that reactivity of halogens decreases down the group.
Hence, we can say that, the reactivity of halogens is \[{{\rm{F}}_{\rm{2}}} > {\rm{C}}{{\rm{l}}_2} > {\rm{B}}{{\rm{r}}_2} > {{\rm{I}}_{\rm{2}}}\].

Thus, the correct option is D.

Note:
The formation of hydrogen halides occurs with the help of covalent bonding. So we can say that the order of reactivity is just opposite to the order of acidity of the resulting acids. Among the halogens, hydrogen iodide is the strongest acid. It has the largest size due to which the bond length increases and bond strength decreases. Therefore, it easily loses protons and acts as a strong acid.