Question

Explain the following, give an appropriate reason.

The electron affinity values of Be and Mg are almost zero and those of N (0.02 eV) and P (0.80 eV) are very low.

Answer 1

Be (Z = 4) 1s² 2s²

Mg (Z = 12) 1s² 2s² 2p⁶ 3s²

Noble gases have the electronic configuration of ns² np⁶. All these are completely filled and are more stable. For all these elements Be, Mg and noble gases, the addition of electrons is unfavorable and so they have zero electron affinity.

Nitrogen (Z = 7) 1s² 2s² 2p_x¹ 2p_y¹ 2p_z¹.

It has a half-filled electronic configuration. So the addition of electrons is unfavorable and it has a very low electron affinity value of 0.02 eV.

Phosphorus (Z = 15) 1s² 2s² 2p⁶ 3s² 3p_x¹ 3p_y¹ 3p_z¹.

It also has a half-filled electronic configuration. Due to the symmetry and more stability, it has a very low electron affinity value of 0.80 eV.