The observed disparity in freezing points between xenon and helium, both noble gases, stems primarily from the strength of their intermolecular forces. Helium, being a very small and light atom, exhibits exceptionally weak London dispersion forces. These forces arise from temporary fluctuations in electron distribution, creating transient dipoles that induce dipoles in neighboring atoms. The feeble nature of these interactions translates to a remarkably low freezing point.
Xenon, in contrast, possesses a significantly larger atomic size and a greater number of electrons. This larger electron cloud makes xenon far more polarizable. Consequently, the temporary dipoles formed are more pronounced, leading to stronger London dispersion forces between xenon atoms. The increased strength of these attractive forces necessitates a lower temperature to overcome them and transition from a liquid to a solid state. This highlights the direct relationship between atomic size, polarizability, intermolecular forces, and freezing point.
