Question

Which factor is most responsible for the increase in boiling points of noble gases from $He$ to $Xe$ ?
A. Decrease in IE
B. Monoatomic nature
C. Decrease in polarisability
D. Increase in polarisability

Answer 1

The factor which is most responsible for the increase in boiling points of noble gases is their increase in the ability of the electron cloud to distort easily in the influence of the electric field. This is called polarizability and it increases with increase in size.

Complete answer:
As we move from helium to xenon, we see that the atomic radii increases steadily due to an increase in the number of electrons as they move from one period to another period. The size of the atom is related to several properties of noble gases.
The ionization potential of noble gas is inversely proportional to the atomic radius. Thus on moving from helium to xenon the ionisation energy decreases as the atomic size increases. But this is not the most responsible reason for higher boiling point.
As the valence electrons in the larger noble gases are away from the nucleus. So, they are held less tightly by the atom. So we can say that the attractive force increases as the size of the atom increases. Due to an increase in attractive force polarizability will also increase.
So, increase in polarizability is the most responsible factor for the increase in boiling points of helium to xenon.
In simple words, as the size or atomic radii increases from helium to xenon then the polarizability also increases with increase in size. It causes the increase in boiling point of noble gas from helium to xenon.

Hence, option D is correct.

Note:
Helium is generally used as a component of breathing gases. Because it has low solubility in fluids or lipids. This is especially used during scuba diving because other gases are absorbed by the blood and body tissues when under pressure during scuba diving.