Question

among p,s, cl which have least negative electron gain enthalpy value and why

Answer 1

When an electron is added, if the element is stabilized it releases a lot of energy (exothermic)

Least negative electron gain enthalpy implies lesser energy is emitted i.e not much stability is achieved on addition of an electron.

P,S and Cl try to achieve octet configuration by accepting electrons.

Number of electrons required to achieve stability is 3,2 and 1.

Hence P is not much stabilized in comparison to others. So it has least negative electron gain enthalpy value while Cl has most negative electron gain enthalpy value