Electron configuration of copper
What is the ground-state electron configuration of copper (Z = 29)?
Answer B: explanation for every choice
A
This is the predicted filling order, but copper is an exception.
B
Correct. Promoting one 4s electron gives a stable, completely filled 3d subshell.
C
This has 30 electrons, the configuration of zinc.
D
A d subshell holds at most 10 electrons.
TakeawayCu and Cr are exceptions: filled or half-filled d subshells are favored.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID cp97.