Name: Dual Nature of Light and Matter
Uploaded: 2019-07-19
Duration: 7 min 31 s
Description: Light has a dual nature. It is both a wave and a particle. Explore this video about the wave and particle nature of light and the wavelength corresponding to...

Question

Illustrate the reasons for the stability of completely filled and half filled subshells.

Accepted Answer

The stability of completely filled and half filled subshells are due to the following reasons:

1. Symmetrical distribution of electrons: It is well known that symmetry leads to stability. The completely filled or half filled subshells have symmetrical distribution of electrons in them and are therefore more stable.

2. Exchange energy: The stabilising effect arises whenever two or more electrons with the same spin are present in the degenerate orbitals of a subshell. These electrons tend to exchange their positions and the energy released due to this exchange is called exchange energy. The number of exchanges that can take place is maximum when the subshell is either half filled or completely filled. As a result the exchange energy is maximum and so is the stability.

It may be noted that the exchange energy is at the basis of Hund’s rule that electrons which enter orbitals of equal energy have parallel spins as far as possible. In other words, the extra stability of half-filled and completely filled subshell is due to:
(i) relatively small shielding,
(ii) smaller coulombic repulsion energy, and
(iii) larger exchange energy.

Illustrate the reasons for the stability of completely filled and half filled subshells.

Important Questions on Atomic Structure

Learn and Prepare for any exam you want !