Which one of the following is the correct electronic configuration of copper?
1s²2s²2p⁶3s²3p⁶3d¹⁰4s¹
1s²2s²2p⁶3s²3p⁶3d⁹4s²
1s²2s²2p⁶3s²3p⁶3d¹⁰4s²
1s²2s²2p⁶3s²3p⁶3d⁸4s²
Answer is Wrong!
Answer is Right!
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UPSC Geoscientist – 2023
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.