Study Notes on Transition Metals and Electron Configuration

Introduction to Transition Metals

  • Transition metals are the elements located between the s-block and p-block of the periodic table.
  • The periodic table is divided into blocks:
    • s-block: Groups 1 and 2 (e.g., lithium, magnesium)
    • p-block: Begins with boron and includes noble gases.
  • Transition metals, identified as the d-block, contain d electrons in their configurations.
  • Inert transition metals include lanthanides and actinides (labelled in purple).
    • Distinction is made between transition elements and inner transition elements.

Properties of Transition Metals

  • Share properties with main group metals:
    • Good conductors of electricity
    • Similar physical characteristics
  • Key differences include presence of d electrons and formation of ions with multiple charges:
    • Ions can be positive or negative, depending on the number of lost or gained electrons.
    • Transition metals can form ions with multiple oxidation states, while main group metals generally form ions with specific charges.

Electron Orbitals

  • Types of Electron Orbitals:
    • s: 1 orbital (max 2 electrons)
    • p: 3 orbitals (max 6 electrons)
    • d: 5 orbitals (max 10 electrons)
  • Energy Levels: There are seven energy levels corresponding to periods on the periodic table:
    1. Period 1: 1s
    2. Period 2: 2s, 2p
    3. Period 3: 3s, 3p
    4. Period 4: 4s, 3d (D orbitals start filling here)
    5. Period 5: 5s, 4d
    6. Period 6: 6s, 5d
    7. Period 7: 7s, 6d

Electron Configuration of Transition Metals

  • Transition metals use the short notation featuring noble gas configurations.

  • For Fourth Period Transition Metals:

    • Use argon as the noble gas reference:
    • General form: [Argon] 4s² 3d^x,
    • Where x represents the number of electrons in the d orbital.

  • Example: Scandium (element 21):

    • Electron Configuration: [Ar] 4s² 3d¹

  • For Fifth Period Transition Metals:

    • Use krypton as the noble gas reference:
    • General form: [Krypton] 5s² 4d^x.

  • Example: Zirconium (element 40):

    • Electron Configuration: [Kr] 5s² 4d²

Filling Order of Electron Orbitals

  1. Start electron filling with lower energy orbitals first:
    • Example Transition from Argon to Scandium:
      • Argon: 1s² 2s² 2p⁶ 3s² 3p⁶ (total 18 electrons)
      • Create higher energy levels for 4s and 3d as elements increase.
  2. When adding electrons, ensure the total matches the atomic number of the element.

Specific Examples of Electron Configuration

  • Titanium (element 22):
    • Configuration: [Ar] 4s² 3d² (18 + 2 + 2 = 22 electrons)
  • Chromium (element 24):
    • Expected: [Ar] 4s² 3d⁴
    • Corrected Configuration: [Ar] 4s¹ 3d⁵ (electrons move for stability into half-filled d orbitals)
  • Copper (element 29):
    • Expected: [Ar] 4s² 3d⁹
    • Corrected Configuration: [Ar] 4s¹ 3d¹⁰ (completely filled d orbitals are more stable)

Stability and Electron Exception Principles

  • The movement of electrons from s to d orbitals for stability leads to exceptions:
    • Chromium: 4s¹ 3d⁵ instead of 4s² 3d⁴
    • Copper: 4s¹ 3d¹⁰ instead of 4s² 3d⁹
  • When predicting electron configurations, remember some elements may not follow expected patterns due to stability factors.

Further Elements Considerations

  • For gallium (element 31):
    • Configuration: [Ar] 4s² 3d¹⁰ 4p¹
  • For cadmium (element 50):
    • Correct Configuration: [Kr] 5s² 4d¹⁰
  • Importance of ensuring the total number of electrons matches the atomic number throughout calculations.

Conclusion

  • Transition metals have unique electron configurations influenced by the d orbitals and stability preferences. Understanding the filling order, exceptions, and properties is essential for the study of these elements in chemistry.