Answer to Question #76656 in Inorganic Chemistry for Dawa Doma Sherpa

Question

Although the 4s orbitals are occupied before 3d orbitals, yet we cannot say that they are always more stable. Explain with suitable examples.

Answer 1

4s orbitals have low energy compare to 3d orbitals. In orbital electron filled by (n+l) rule. According to (n+l) rule which orbital taking have low energy, filled firstly.

But sometime also 3d orbitals may be more stable although it's energy high compare to 4s orbitals. Because according to Hund`s rule half filled orbitals are more stable.

In this case having high energy orbitals more stable compare to having low energy orbitals. For example, 4p3 orbital is more stable compare to 3d2 orbital.