The correct electronic configuration of chromium (Z = 24) is
Correct answer: B. [Ar] 3d5 4s1
- A. [Ar] 3d4 4s2
- B. [Ar] 3d5 4s1
- C. [Ar] 3d6 4s0
- D. [Ar] 3d3 4s3
Explanation
Chromium promotes one 4s electron into the 3d subshell because a half filled d5 configuration alongside a half filled 4s is more stable than d4 with a full 4s. Copper does the same thing to reach a full d10. The 4s subshell can never hold three electrons, which rules out the last option outright.
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About Electronic Configuration
Electronic configuration describes how electrons occupy shells, subshells and orbitals around an atom. Questions use the Aufbau principle, Pauli exclusion principle and Hund's rule to write configurations, identify valence electrons, form ions and explain periodic trends, including common exceptions such as chromium and copper.
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