As shown in Fig. , using Argon as an example of inert gases, the operation number, n, of p 6 atomic orbital is 6+1 (1 denotes E operation). Assuming that each operation contributes 1/2 RT to either the rotational kinetic energy or the entropy of the ensemble, n/2=3.5 is close to the A value of Ar, 2.9104. This means that 0.5896 RT remains in the liquid, assuming that a molecule in the gas state is entirely free and owns all the operation numbers. It turns into rotational and translational energy in the liquid state, even though most operations are restricted due to the dense packing of molecules. Similarly, for Ne, Kr, and Xe, the values of n/2-A are 0.9492, 0.5896, 0.586, and 0.5822, respectively. It implies that the smaller the atom, the more energy remains. In other words, the larger the atom, the tighter the packing in the liquid. It is consistent with the density variation.