Question

The noble gas which behaves abnormally in liquid state is
A.$Xe$
B.$Ne$
C.$He$
D.$Ar$

Answer 1

Hint: Noble gases are inert gases which have very low reactivity and high stability as they have fully filled shells. They are colourless and non flammable gases which appear as ideal gases. The abnormal behaviour shown by the liquid form of a noble gas is the presence of properties of a gas even though it is in liquid state.

Complete step by step answer:
The six naturally occurring gases of the group 18 are known as noble gases. These include helium, argon, krypton, xenon and radon which is radioactive. They are colourless and non flammable gases at room temperature and are known as noble gases as they have extremely low reactivity due to their high stability and they have a configuration in which the electron shells are filled. These are known as inert or rare gases. Under standard conditions, they appear to be ideal gases with low melting and boiling points.
When a liquid isotope of helium is cooled it changes into a liquid from a gas and thus, change of state takes place. Further when this liquid is cooled it shows the properties of a gas even when it is in a liquid state and thus, this behaviour of helium is said to be abnormal as helium takes the form of a superfluid which flows without resistance.
Helium does not freeze at atmospheric pressure. Liquid helium is formed after a continuous process of compressing the helium gas and then expelling it which expands the gas and it then cools down.Therefore, we conclude that the correct option for the above question is $He$.

Hence option C is correct.

Note:
Liquid helium is said to be the coldest material and is considered as the only element which does not exist as a solid. Liquid helium is used as a refrigerant and the superfluid form of helium gas was used as a satellite to gather information about infrared waves and it is also in machines which are used to report information regarding gravity.