What are factors which influence the electron gain enthalpy ?

Explanation

Factors influencing electron gain enthalpy :
(i) Size of the atom : Electron affinity is inversely proportional to the size of the atom .As the size of atom increases , the effective nuclear charge decreases or the nuclear attraction for adding electron decreases.
(ii) Nuclear charge : Electron affinity is directly proportional to effective nuclear charge Greater the nuclear charge more will be the tendency to accept electrons so Electron affinity is more .
(iii) Electronic configuration : An atom with stable electronic configuration has no tendency to gain an electron . Such atoms have zero or almost zero electron gain enthalpy.
(iv) Shielding effect : Electron affinity is inversely proportional to shielding effect . Electronic energy state , lying between nucleus and outermost state hinder the nuclear attraction for incoming electron . Therefore , greater the number of inner lying state , less will be the electron affinity.