Exceptions of Aufbau Principle
There are a few exceptions to the Aufbau Principle which are Chromium and Copper. Their electronic configuration is,
Electronic Configuration of Chromium
The electronic configuration of Chromium according to the Aufbau Principle should be
- Cr(24): [Ar]3d44s2
But the above configuration is not correct because the actual electronic configuration of Chromium(Cr) is,
- Cr(24): [Ar]3d54s1
The reason for this electronic configuration is that the half-filled d-atomic orbital is more stable than the orbital filled according to the Aufbau Principle.
Electronic Configuration of Copper
The electronic configuration of Copper according to the Aufbau Principle should be,
- Cu(29): [Ar]3d94s2
The above configuration is not correct because the actual electronic configuration of Copper(Cu) is,
- Cu(29): [Ar]3d104s1
The reason for this electronic configuration is that the full-filled d-atomic orbital is more stable than the orbital filled according to the Aufbau Principle.
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Aufbau Principle
Aufbau Principle is the basic method that tells us how the electrons are filled in the atomic orbital. According to the Aufbau Principle, the filling of the electrons in the ground state of an atom follow a basic pattern. This principle tells us that the electrons in the atomic orbital of any atoms are filled in the ascending order of their energy and for finding the energy of the atomic orbital they follow the “n+l” rule.
In this article, we will learn about Aufbau Principle, Features of the Aufbau Principle, its exceptions and limitations in detail.