Introduction to Transition Metal Chemistry:

1.1. Electronic Configuration of Transition Elements

The list of the first two rows of transition elements with their corresponding electronic configurations is tabulated below. It can be noted that in some of these elements, the configuration of electrons corresponds to (n-1)d⁵ ns¹ or (n-1)d¹⁰ ns¹. This is because of the stability provided by the half-filled or completely filled electron orbitals.

It can be observed that the Aufbau principle is not followed by many transition elements like chromium. The reason for this is believed to be the relatively low energy gap between the 3d and 4s orbitals, and the 4d and 5s orbitals.