Landon - Study Notes on Exceptions in Electron Configurations

Exceptions with Electron Configurations

• Discusses exceptions in electron configurations that occur with partially and half-filled sublevels.

• Key focus: Elements copper (Cu) and silver (Ag).

Stability of Sublevels

• Filled sublevels are generally more stable than partially filled sublevels.

• Importance in the context of d orbitals during the filling of electrons.

Copper (Cu)

• Atomic number: 29.

• Standard electron configuration:

  • Argon (Ar) core configuration followed by:

  • $4s^2 3d^9$

• Characteristics:

  • Contains 1 unpaired electron in the higher energy 3d sublevel.

• More stable electron configuration:

  • Copper modifies its configuration for stability:

    • Takes one electron from the 4s shell and completes the 3d shell:

    • Resulting configuration: $Ar 4s^1 3d^{10}$

  • Advantage of this arrangement:

    • A fully filled 3d sublevel is more stable despite higher energy.

Silver (Ag)

• Atomic number: 47.

• Electron configuration using shorthand notation (Noble gas core):

  • Krypton (Kr) followed by:

  • $5s^2 4d^9$

• Characteristics:

  • Paired electrons in the 5s orbital.

  • 4d sublevel contains only 9 electrons, resulting in an unpaired electron.

• More stable electron configuration:

  • Silver also modifies its electron configuration for stability:

    • Takes one electron from the 5s shell to fill the 4d shell:

    • Resulting configuration: $Kr 5s^1 4d^{10}$

    • The 4d sublevel’s higher energy makes the filled state more favorable than having an unpaired electron.

Conclusion

• Both copper and silver deviate from the expected electron configurations due to their higher stability when d sublevels are fully filled.

• The presence of unpaired electrons in higher energy levels contributes to instability, driving the elements to prefer configurations that lead to lesser energy states through their natural adaptions in electron configurations.