Electron gain enthalpy, (EGE) increases in period from left to right and decreases in group on moving downward. E.G.E
B.C.N,O.F
Electron‌gain‌enthalpy‌increases
(G=17)(G=15)
F
N
Cl
P
Br
As
I
Sb
↓ E. G. E decreases Here, in group 17, chlorine having very high electron gain enthalpy (349‌kJ∕mol). Due to high electronegativity of fluorine, it has second high electron gain enthalpy (328‌kJ∕mol). Order of increasing electron gain enthalpy N<P<F<Cl (in kJ∕mol)(7)(72)(328)(349)