Who among the following discovered $Argon$?

The correct order of enthalpy of vaporisation of noble gases is

Noble gases have very low boiling points. Why?

Match the Xenon compounds in Column-$I$ with their structures in Column-$II$ and assign the correct code.

Column-$I$	Column-$II$
$(a) XeF_{4}$	$(i) \text{Pyramidal}$
$(b) XeF_{6}$	$(ii) \text{Square planar}$
$(c) XeOF_{4}$	$(iii) \text{Distorted octahedral}$
$(d) XeO_{3}$	$(iv) \text{Square pyramidal}$

Code: $(a) \quad (b) \quad (c) \quad (d)$

Explain the variations in the following properties of group $18$ elements:
$(i)$ Atomic radii
$(ii)$ Ionisation enthalpy
$(iii)$ Electron gain enthalpy

Which factor is most responsible for the increase in boiling points of noble gases from $He$ to $Xe$?