Inert gases such as helium behave like ideal gases over a wide range of temperature. However, they condense into the solid state at very low temperatures. It indicates that at very low temperature there is a

Solids have strong interactive forces (Van der Waal forces) between them than liquids and gases, therefore atoms in solids are tightly bound with each other and cannot leave their lattice site. In low temperature, He condenses at room temperature which indicates that there is strong attractive forces between He atoms. These Van der Waal forces depends on the size of atom. The more is the size of atoms, the more is the Van der Waal forces and this results in increasing in the polarizability of atoms.