Question

Which of the following halides is least stable and has doubtful existence?
A. $C{{I}_{4}}$
B. $Sn{{I}_{4}}$
C. $Ge{{I}_{4}}$
D. $Pb{{I}_{4}}$

Answer 1

Hint: In this question, we have to know the properties of halides. Lead iodide is the least stable due to the large size and it has a doubtful existence due to its strong oxidising nature.

Complete Step by Step Solution:
To answer this question, we must know the properties of halides:-
We know halides are group 17 elements and have the general configuration is $n{{s}^{2}}n{{p}^{5}}$

Atomic and Ionic Radii : halogens have the smallest atomic radii due to their maximum effective nuclear charge. When we go down the group, atomic and ionic radii continue increasing.

Ionisation Enthalpy : They Have very little tendency to lose electrons, so they have high ionisation enthalpy. When we go down the group, Ionisation enthalpy decreases due to increase in size.

Electron gain Enthalpy : Halogens are near to gain stability as they need only electrons to have stable noble gas configuration. When we go down the group, enthalpy goes on decreasing but the enthalpy of fluorine is less than chlorine due to its small size and high electronic repulsion.

So as we discuss when we go down the group the stability of halides goes on decreasing due to increase in the size of atoms, because of that halogens easily dissociates from the compound.

So, we say that lead iodide is the least stable among the halides group.
Due to the strong oxidising nature of $Pb^{4+}$, it experiences a doubtful existence.
Thus, Option (D) is correct.

Note: In the halide group, another element known as astatine exists which exists as a radioactive element. Students must know the knowledge of halides to answer this question.