As far as I know, to non-polar molecules like CF4 and C2H6, boiling point is mainly affected by the London dispersion force.
As a result, molecules with more protons and electrons normally have higher boiling points.
However, CF4 (34 electrons) has a boilng point of -128°C, while C2H6 (18 electrons) has -89°C.
Also, I find it puzzling that fluorides tend to have abnormally low boiling points.
For example (the below are all boiling points of compounds with a benzene ring)
C6H6 80.1 °C
C6F6 80.2 °C
C6Cl6 322 °C
C6Br6 418 °C
C6I6 531 °C
It seems to me that fluorides are the abnormal ones. Despite having a lot more electrons than benzene, the boiling point is almost the same.
Is there something I'm missing?