Explain why transition elements have many irregularities in their electronic contigurations.

Explanation

In transition elements, (n - 1)d and ns orbitals have very small difference in energy. Also, electrons occupying half-filled or completely filled d-subshell have increased stability. Keeping in view the above facts, it is easy to understand that the incoming electron may enter into ns or (n -1)d subshell. Hence transition elements show irregularities in their electronic configurations.