Which one of the following is the correct electronic configuration of

Which one of the following is the correct electronic configuration of copper?

[amp_mcq option1=”1s²2s²2p⁶3s²3p⁶3d¹⁰4s¹” option2=”1s²2s²2p⁶3s²3p⁶3d⁹4s²” option3=”1s²2s²2p⁶3s²3p⁶3d¹⁰4s²” option4=”1s²2s²2p⁶3s²3p⁶3d⁸4s²” correct=”option1″]

This question was previously asked in

UPSC Geoscientist – 2023

Download PDF Attempt Online

Copper (Cu) has an atomic number of 29. The Aufbau principle and Hund’s rule predict the filling of orbitals in increasing order of energy. The expected electronic configuration based on the strict Aufbau principle would be 1s²2s²2p⁶3s²3p⁶4s²3d⁹.
However, elements like Copper (and Chromium) are exceptions to this rule. There is a slight energy difference between the 4s and 3d orbitals. The configuration with a completely filled or half-filled d subshell is more stable than one that is nearly filled.
In the case of Copper, promoting one electron from the 4s orbital to the 3d orbital results in the configuration 1s²2s²2p⁶3s²3p⁶3d¹⁰4s¹. This configuration has a stable, completely filled 3d subshell and a half-filled 4s subshell, which is energetically more favorable than the 3d⁹4s² configuration.
Therefore, the correct electronic configuration of copper is 1s²2s²2p⁶3s²3p⁶3d¹⁰4s¹.

Copper is an exception to the standard Aufbau principle; its ground state electronic configuration involves the transfer of an electron from the 4s to the 3d orbital to achieve a more stable completely filled 3d subshell.

Other elements exhibiting similar exceptions include Chromium (Cr, Z=24) with configuration [Ar] 3d⁵ 4s¹ instead of [Ar] 3d⁴ 4s². These exceptions highlight the complex interplay of electron-electron repulsion and orbital energies.

More similar MCQ questions for Exam preparation:-