TITLE: Reason for a small difference between boiling and melting temperatures of some gases
QUESTION [4 upvotes]: Some gases has very low difference between boiling and melting temperatures, like $\Delta T \leq 6~ \text{K}$ :
$$
\text{Helium},~   \{~T_m,T_b\} =\{0.95 K  , 4.222 K\} \\
\text{Neon},~     \{~T_m,T_b\} =\{24.56 K , 27.104 K\} \\
\text{Argon},~    \{~T_m,T_b\} =\{83.81 K , 87.302 K\} \\
\text{Hydrogen},~ \{~T_m,T_b\} =\{13.99 K , 20.271 K\}
$$
But others starts accumulating more heat, while transitioning to next boiling phase, like $\Delta T \geq 14~ \text{K}$ :
$$
\text{Nitrogen},~  \{~T_m,T_b\} =\{63.15 K , 77.355 K\}\\
\text{Fluorine},~   \{~T_m,T_b\} =\{53.48 K , 85.03 K\} \\
\text{Oxygen},~     \{~T_m,T_b\} =\{54.36 K , 90.188 K\}\\
\text{Chlorine},~   \{~T_m,T_b\} =\{171.6 K , 239.11 K\}
$$
Question,- Why first group of gases has comparatively low temperature threshold for transitioning from melting to boiling state ? My gut feeling tells me that it may be somehow related to electron configuration and degrees of freedom, but I'm not able to map exact causes.

REPLY [3 votes]: This is more of a chemistry question but anyway in the gases in the first group there are no strong intermolecular forces acting this means that the molecules can easily be seperated. The only forces in the first set are weak vander waal forces.
Note that these are not just governing factors most of the time the high melting point indicates ease of being in solid state due to there size and symmetry for example in argon. The low boiling point implies that surface area of liquids is less or molecules are weakly hold together in liquid phase. Whenever a molecule has less surface area and high tendency for close packing tend to have very little difference in there melting and boiling points some times the difference is so small that we see it subliming.
Most important thing is to say is that two different properties determine the melting and boiling points of molecules so you cannot always compare them using one property such degree of freedoms or electronic configuration.
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