Question

The stabilisation of a half-filled d-orbital is more pronounced than that of the p-orbital why?

Answer 1

The exactly half-filled orbitals have greater stability. The reason for their stability are –

1. symmetry
2. exchange energy.

1. Symmetry: The half-filled orbitals are more symmetrical than partially filled orbitals and this symmetry leads to greater stability.

2. Exchange energy: The electrons with the same spin in the different orbitals of the same sub-shell can exchange their position. Each such exchange releases energy and this is known as exchange energy. Greater the number of exchanges, the greater the exchange energy, and hence greater the stability. In d-orbital, 10 exchanges are possible but in p-orbital 6 exchanges are possible. So, d-orbital with 5 unpaired electrons (10 exchanges)n i.e. half-filled is more stable than p-orbital with 3 unpaired electrons (6 exchanges).