Question

Why is interhalogen compound $IC{{l}_{3}}$ more reactive than halogen ${{I}_{2}}$?

Answer 1

Bonds with partial ionic character will be weaker than covalent bonds. Molecules with weaker bonds will have lesser bond dissociation energy. Molecules with lesser bond dissociation energy will be more reactive.

Complete step-by-step answer: - Let us first understand the fact that $IC{{l}_{3}}$ is an interhalogen compound. An interhalogen compound is basically a compound that contains 2 or more different halogen atoms. It is important to note that interhalogen compounds do not contain atoms of elements from any other groups.
- ${{I}_{2}}$ is a halogen existing in its natural form. Halogens are the set of six non-metallic elements that belong to the 17th group of the periodic table. They belong to the same group as they have similar chemical and physical properties.
- In the interhalogen compound$IC{{l}_{3}}$, the less electronegative iodine is bonded with the more electronegative chlorine atoms. Due to this difference in electronegativity, there will be a partial ionic character which will cause the I – Cl bond in $IC{{l}_{3}}$ will be weak.
- In the halogen ${{I}_{2}}$, both the atoms of iodine will have the same electronegativity. Hence ${{I}_{2}}$ will form a strong covalent bond between the iodine atoms.
- The covalent bond between the iodine atoms of the halogen will obviously be stronger than the I – Cl bond in $IC{{l}_{3}}$which has partial ionic character.
- Hence we can say that the bond dissociation energy of $IC{{l}_{3}}$ will be lesser than that of ${{I}_{2}}$. This means that $IC{{l}_{3}}$ is less stable compared to ${{I}_{2}}$.
- We know that a more stable compound will be less reactive.
- Hence, we can conclude that the less stable $IC{{l}_{3}}$ will be more reactive than the stable ${{I}_{2}}$.

Note: Interhalogen compounds are always more reactive and less stable than halogens. This stays true irrespective of the number of atoms in the interhalogen compound. This is because covalent bonds are stronger than ionic bonds.