Chromium and copper have anomalous electronic configurations because
Correct answer: B. a half filled or completely filled d subshell is more stable
- A. their nuclei are unstable
- B. a half filled or completely filled d subshell is more stable
- C. they lose electrons easily
- D. the 4s orbital does not exist for them
Explanation
Promoting one 4s electron gives chromium a 3d5 4s1 arrangement and copper a 3d10 4s1 arrangement, both of which gain stability from the symmetry and reduced repulsion of a half filled or full subshell. These two exceptions are examined far more often than the rule itself. The energy gap between 4s and 3d is small enough for the swap to be worthwhile.
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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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