Electron Configurations and d Orbitals

Review of Potassium and Calcium

1. Potassium (K) Configuration: 4th Period

   • Noble Gas Notation: [Ar]4s¹
   • Potassium (19 electrons): Extra electron in the 4s orbital
   • Energy Levels: 4s < 3d (4s is lower in energy than 3d)

2. Calcium (Ca) Configuration

   • Noble Gas Notation: [Ar]4s²
   • Calcium (20 electrons): Two additional electrons in the 4s orbital

3. Calcium Ion (Ca²⁺) Configuration

   • Electron Configuration: Same as Argon [Ar]
   • Formation: Lose two electrons from the 4s orbital

Transition to d Orbitals

4. Scandium (Sc) Configuration: Periodic Table Insights

   • Scandium (21 electrons): 3 electrons after Argon
   • Energy Change: 4s orbital becomes higher in energy than 3d orbital
   • Noble Gas Notation: [Ar]4s²3d¹
   • Ionization Proof: From ionization experiments confirming the 4s orbital is higher in energy
   Electron Configuration of Scandium: - [Ar]4s²3d¹ or [Ar]3d¹4s² ``

Trends and Anomalies in d Orbitals

5. Titanium (Ti) Configuration

   • Titanium (22 electrons): [Ar]4s²3d²

6. Vanadium (V) Configuration

   • Vanadium (23 electrons): [Ar]4s²3d³

7. Chromium (Cr) Configuration: Anomaly

   • Chromium (24 electrons): [Ar]4s¹3d⁵ (Expected [Ar]4s²3d⁴)
   • Explanation: Stability associated with half-filled d subshell

8. Manganese (Mn) Configuration

   • Manganese (25 electrons): [Ar]4s²3d⁵

9. Iron (Fe) Configuration

   • Iron (26 electrons): [Ar]4s²3d⁶

10. Cobalt (Co) Configuration

    • Cobalt (27 electrons): [Ar]4s²3d⁷

11. Nickel (Ni) Configuration

    • Nickel (28 electrons): [Ar]4s²3d⁸

12. Copper (Cu) Configuration: Anomaly

    • Copper (29 electrons): [Ar]4s¹3d¹⁰ (Expected [Ar]4s²3d⁹)
    • Explanation: Stability associated with filled d subshell

13. Zinc (Zn) Configuration

    • Zinc (30 electrons): [Ar]4s²3d¹⁰

Summary

• General Trend: 4s fills before 3d, but post Scandium, the 4s orbital has a higher energy and electron configurations can show anomalies due to stability considerations and ionization experiments.
• Practical Tip: Despite complexities, use periodic table as a guide for quick electron configuration during tests.