Question

What is decreasing order of electron gain enthalpy of N, P, As, Sb, Bi?

Answer 1

Dear student,

Electron gain enthalpy is the minimum amount of energy released when an extra electron is added to the valence shell of
isolated gaseous atom in the ground state resulting in the formation of uninegative ion.
In group 15 all the elements have half filled p orbital in the ground state hence, they are stable already.
Whenever an extra electron is added in the stable ground state then , the value for electron gain enthalpy will be positive (endothermic process )
Electron gain enthalpy is inversely proportional to the atomic radius.
The order for electron gain enthalpy is = P > N > As> Sb > Bi
There is one exception in the order that the electron gain enthalpy of nitrogen is less than phosphorous because of smaller size of valence shell of nitrogen than phosphorous.
The electron density is higher in nitrogen so, provide repulsion to the incoming electron more than phosphorous therefore, following order is observed.

Regards