Question

Which inert gas has the highest boiling point?
(A) Xe
(B) Ar
(C) Kr
(D) He

Answer 1

Hint:
Complete step by step solution:
The inert gases exist as monatomic in nature under standard conditions. As their outer shell is completely filled, making it extremely stable. Due to which there is a presence of weak interatomic forces in them. But with the increase in the size of the inert gases down the group, this interatomic force weakens and the attractive force due to the increase in the electron-cloud takes place.
With the increase in the size of the atom down the group, the electrons are loosely bound to the nucleus as the effective nuclear charge decreases. This leads to the atom to become slightly polar as the electrons can easily disperse. Thus, causing polarizability (dipoles) and the presence of weak Van der Waals dispersion force of attraction.
The polarizability increases with the increase in the electron-density of the atom. So, down the group, with the increase in size with the addition of new shells, the polarizability increases. Hence, the instantaneous dipoles can be induced easily to the neighbouring atom, leading to an increase in the Van der Waals force.
The Van der Waals force is related to the boiling point. With the increase in the dispersion force, the boiling point increases.
Therefore, the Xenon atom with the largest size has more dispersion forces present and highest boiling point among the inert gases.

Answer is opton (A).

Note: The boiling point of inert gases are very low compared to the other elements in the periodic table with the same atomic or molecular mass, as they have very stable configuration and weak dispersion force present in the solid or liquid state.