Question

Explain in detail the extra stability of 4s^1 3d^10 configuration of Cu with respect to symmetry and exchange energy.

Answer 1

Exceptional electronic configuration arises because of the extra stability due to the half filled and fully filled electronic configuration.

Half filled and fully filled electronic configuration have extra stability due to two factors:

1) Symmetrical arrangement

2) Stability due to the exchange energy.

Half filled and fully filled electronic configuration have large exchange energy and consequently have greater stability.

For example in 3d series of the transition metals exceptional electronic configuration is shown by Cr (atomic number24)and Cu (atomic number29).

Cr = 3d5 4s1 (both d and s orbitals are half filled so they are symmetrical and posses large exchange energy).

Cu = 3d104s1 (d orbital is fully filled and s orbital is half filled leading to symmetry and greater exchange energy).