Uploaded August 2025 | Updated September 2026, 2 weeks ago
Orbital Configuration Anomalies
Orbital Anomalies in Electron Configurations
In atomic chemistry, orbital anomalies refer to cases where elements deviate from the expected electron configuration based on the Aufbau principle.
These anomalies usually occur in transition metals and are driven by stability preferences for half-filled or fully-filled subshells.
Why Do These Anomalies Occur?
Exchange energy: Parallel spins in half-filled orbitals reduce repulsion.
Symmetry and stability: Half-filled and fully-filled subshells are energetically favorable.
Electron-electron interactions: Can shift orbital energies slightly, making unexpected configurations more stable.
Chromium (Cr)
Expected: [Ar] 4s² 3d⁴
Actual: [Ar] 4s¹ 3d⁵
Reason: A half-filled 3d⁵ subshell is more stable than 3d⁴.
Copper (Cu)
Expected: [Ar] 4s² 3d⁹
Actual: [Ar] 4s¹ 3d¹⁰
Reason: A fully-filled 3d¹⁰ subshell is more stable than 3d⁹.
Molybdenum (Mo)
Expected: [Kr] 5s² 4d⁴
Actual: [Kr] 5s¹ 4d⁵
Silver (Ag)
Expected: [Kr] 5s² 4d⁹
Actual: [Kr] 5s¹ 4d¹⁰
Link to Lecture Slides: drive.google.com/file/d/1zokEkS3zmbHSFitt6Sss_Vpj7RRbMI1w/view?usp=drive_link
*Due to the description character limit the full work cited for "Orbital Configuration Anomalies" can be viewed at... docs.google.com/document/d/1QrDA6qej4XieVNh1TQOucFRhk9woWG8h/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true
Orbital Configuration Anomalies
Orbital Anomalies in Electron Configurations
In atomic chemistry, orbital anomalies refer to cases where elements deviate from the expected electron configuration based on the Aufbau principle.
These anomalies usually occur in transition metals and are driven by stability preferences for half-filled or fully-filled subshells.
Why Do These Anomalies Occur?
Exchange energy: Parallel spins in half-filled orbitals reduce repulsion.
Symmetry and stability: Half-filled and fully-filled subshells are energetically favorable.
Electron-electron interactions: Can shift orbital energies slightly, making unexpected configurations more stable.
Chromium (Cr)
Expected: [Ar] 4s² 3d⁴
Actual: [Ar] 4s¹ 3d⁵
Reason: A half-filled 3d⁵ subshell is more stable than 3d⁴.
Copper (Cu)
Expected: [Ar] 4s² 3d⁹
Actual: [Ar] 4s¹ 3d¹⁰
Reason: A fully-filled 3d¹⁰ subshell is more stable than 3d⁹.
Molybdenum (Mo)
Expected: [Kr] 5s² 4d⁴
Actual: [Kr] 5s¹ 4d⁵
Silver (Ag)
Expected: [Kr] 5s² 4d⁹
Actual: [Kr] 5s¹ 4d¹⁰
Link to Lecture Slides: drive.google.com/file/d/1zokEkS3zmbHSFitt6Sss_Vpj7RRbMI1w/view?usp=drive_link
*Due to the description character limit the full work cited for "Orbital Configuration Anomalies" can be viewed at... docs.google.com/document/d/1QrDA6qej4XieVNh1TQOucFRhk9woWG8h/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true










