Question

What is electron gain enthalpy how does it varies down a group?

Answer 1

Electron Gain Enthalpy is the energy released when one mole of electron are added to gaseous atoms of an element.Electron Affinity is the same as Electron Gain Enthalpy but viewed as the energy supplied to the surroundings rather than that released by the atoms. Hence its sign is opposite from the latter.
The tendency of an atom to attract the shared pair of electrons towards itself isknown as electronegativity. Electronegativity increases across a period while it decreases down a group. Atomic radius increases down the group due to addition of new shell. ... The atomic radius decreases across a period.