What element in Group 17 is least likely to lose an electron?
We interrogate the process:
In other words we interrogate the ELEMENTAL ionization energy. Note that I know the elements of Group 17 are BIMOLECULAR. But data exist for the ionization process of the ATOMIC gases.
I predict the fluorine will be least likely to lose an electron, on the basis that its measured ionization energy is the largest, i.e. the given reaction is most endothermic. See this site.