Question

Why Group –2 elements have positive electron gain enthalpy?

Answer 1

Heya!!
Group 2 elements such as Berylium, Magnesium, Calcium etc have positive electron gain enthalpies. This is because they are electropositive and need to supplied energy externally if electron is to be added in their already fullfilled s orbital, note that they have an electronic configuration of ns2.

So, group 2 elements have positive electron gain enthalpies

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.