Question

Which of the following noble gases has the highest van der Waals force of attraction?
A. $ Ar $
B. $ Ne $
C. $ Xe $
D. $ He $

Answer 1

Hint: The weak force of attraction which attracts neutral molecules to one another in liquified or solidified gases is known as the Vander Waal force of attraction. There can be three ways through which van der Waal force of attraction may arise i.e., if permanent dipole moment exists between the neutral molecules, interaction of neutral molecules with polar molecules and the force of attraction between neutral molecules at sufficiently low temperature, responsible for condensation of gases into liquid state.

Complete answer:
Generally, the noble gases are monatomic under standard conditions because their outermost shell is completely filled due to which they are extremely stable in nature. Due to this stability, weak interatomic forces exist between them known as van der Waal forces.
As we know that on moving top to bottom in a group, the atomic size of the elements increases due to which the effective nuclear charge decreases down the group i.e., the electrons present in the outermost shell of the element are loosely bound to the nucleus. Therefore, there is a greater tendency for an element to lose electrons and become polar and thus, an increase in the van der Waal force of attraction is observed on moving down the group.
Hence, among the given options xenon has the highest van der Waals force of attraction.
So, option (C) is the correct answer.

Note:
It is important to note that the boiling point of inert gases increases down the group due to an increase in weak intermolecular force of attraction. Therefore, among given options, xenon has a comparatively higher boiling point than other inert gases.