Question

Correct order of oxidising power of halogens is:
A.${\text{B}}{{\text{r}}_{\text{2}}}{\text{ < C}}{{\text{l}}_{\text{2}}}{\text{ < }}{{\text{F}}_{\text{2}}}{\text{ < }}{{\text{I}}_{\text{2}}}$
B.${{\text{F}}_{\text{2}}}{\text{ < }}{{\text{I}}_{\text{2}}}{\text{ < B}}{{\text{r}}_{\text{2}}}{\text{ < C}}{{\text{l}}_{\text{2}}}$
C.${{\text{I}}_{\text{2}}}{\text{ < B}}{{\text{r}}_{\text{2}}}{\text{ < C}}{{\text{l}}_{\text{2}}}{\text{ < }}{{\text{F}}_{\text{2}}}$
D.${{\text{I}}_{\text{2}}}{\text{ > B}}{{\text{r}}_{\text{2}}}{\text{ > C}}{{\text{l}}_{\text{2}}}{\text{ > }}{{\text{F}}_{\text{2}}}$

Answer 1

The oxidising agents are the elements which have a capability of oxidising other by gaining electrons (thus itself gets reduced). And this tendency or ability of gaining electrons is known as oxidising power. An element which has the ability to gain electrons comparatively faster will be a better oxidising agent or has more oxidising power.

Complete step by step answer:
Fluorine (F), Chlorine (Cl), Bromine (Br) and Iodine (I) are together known as halogens and belong to group 17 of the modern periodic table. All of these elements require only one electron to complete their octet and thus are highly electronegative.
Due to their electronegative nature, they have oxidising powers or are good oxidising agents.
Now in a periodic table as we go down the group the electronegativity of the elements decrease. Reason:
This is because of the reason that as we go down the group number of shells around the nucleus increases and thus the valence shell becomes further apart going down the group. Which leads to a decrease in the force of attraction between the nucleus and the valence shell. And because of this the tendency of an atom to attract electrons towards itself also decreases.
Now since electronegativity and oxidising power are directly related to one other as the electronegativity decreases down the group oxidising power also decreases as we move down the group.
And thus the correct order of oxidising power of halogens will be: ${{\text{I}}_{\text{2}}}{\text{ < B}}{{\text{r}}_{\text{2}}}{\text{ < C}}{{\text{l}}_{\text{2}}}{\text{ < }}{{\text{F}}_{\text{2}}}$.
Hence, the correct answer is C.

Note: Please note that halogens are highly reactive because of their high electronegativity and high effective nuclear charge. It is important to note that fluorine is the most electronegative atom in the periodic table. They can be harmful or sometimes even lethal to biological organisms.