Question

which one have more negative value of Electron

Answer 1

Cl has most -ve electron gain enthalpy in periodic table . According to periodicity F should have most -ve electron gain enthalpy , but as the size of F is too small and it has no d orbital, electrons are closely packed which do not allow further addition of electron due to repulsive forces. Cl as larger size than F and presence of d orbitals the electrons are far from each other which makes further addition of electron easier .