1. The electronic configuration of Cr and Cu are [Ar] 3d3 4s1 and [Ar] 3d10 4s1 respectively. The extra stability of half filled and fully filled d orbitals, as already explained in XI STD, is due to symmetrical distribution of electrons and exchange energy.
2. The extra stability of half filled and fully filled d orbitals is due to symmetrical distribution of electrons and exchange energy.
3. When the d orbitals are considered together, they will constitute a sphere. So the half filled and fully filled configuration leads to complete symmetrical distribution of electron density.
4. On the other hand, an unsymmetrical distribution of electron density will result in building up of a potential difference. To decrease this and to achieve a tension free state with lower energy, a symmetrical distribution is preferred.
