Question

Why do 17th group elements have high electron gain enthalpy?

Answer 1

This is because of the steady increment in the nuclear size, which decreases the drive of attraction between the valence electrons and the core electron.

Answer 2

Answer:

1) Halogens (F, C1, Br, I, At) in group 17 have very high negative values of electron gain enthalpy as they acquire stable electronic configuration of noble gas on addition of one electron.

(2) Noble gases in group 18 show high positive values of electron gain enthalpy because the added electron has to enter the next higher shell. This is very unstable electronic configuration. (due to high shielding effect and low effective nuclear charge.)

(3) The alkali metals have very low negative electron gain enthalpy values.