Which of the following will have the most negative electron gain enthalpy and which
the least negative?
P, S, Cl, F. Explain your answer.

Cl has the highest electron gain enthalpy and least is P
remember- as atomic size decreases electron gain enthalpy becomes more negative.
so P is the biggest atom here and F is the smallest
P has the least negative but Cl has the most negative and not the F
Do you know the reason?