Which of the following will have the most negative and least negative electron gain enthalpy? P,S,Cl,F.
Fluorine (F) is the most negative electron gain enthalpy because it is missing one electron to achieve a stable noble gas configuration and therefore is extremely profitable to accept an electron.
Chlorine (Cl) comes next, but its electron gain enthalpy is not as negative as fluorine's because it has a larger atomic radius.
Sulfur (S) has a less negative electron gain enthalpy than chlorine and phosphorus.
(P) has the least negative value since it is also very far from having a stable electron configuration.