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In-Depth Notes on Transition Elements and Their Properties

Transition Elements

  • Definition: Transition elements are found in the d-block of the periodic table, defined by their ability to form one or more stable ions with incomplete d orbitals.

Learning Outcomes

  • After this lecture, you should be able to:
    1. Explain transition elements and their properties.
    2. State electronic configurations for transition elements and their ions.
    3. Describe trends in radii and oxidation states of transition metals.
    4. Determine oxidation numbers and d electron counts in metal complexes.
    5. Recognize and name coordination compounds.
    6. Explain color origin in transition metal complexes due to light absorption.
    7. Discuss ligand exchange reactions, particularly for copper(II) ions with water.

Electronic Configuration of First Row Transition Elements

  • Elements and Their Configurations:
    • Ti (Titanium, 22): 1s^2 2s^2 2p^6 3s^2 3p^6 3d^2 4s^2
    • V (Vanadium, 23): 1s^2 2s^2 2p^6 3s^2 3p^6 3d^3 4s^2
    • Cr (Chromium, 24): 1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^1
    • Mn (Manganese, 25): 1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^2
    • Fe (Iron, 26): 1s^2 2s^2 2p^6 3s^2 3p^6 3d^6 4s^2
    • Co (Cobalt, 27): 1s^2 2s^2 2p^6 3s^2 3p^6 3d^7 4s^2
    • Ni (Nickel, 28): 1s^2 2s^2 2p^6 3s^2 3p^6 3d^8 4s^2
    • Cu (Copper, 29): 1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^1

Characteristics of Transition Elements

  • Properties:
    • Lustrous and shiny metals.
    • Hard and dense due to closely packed structure.
    • High melting and boiling points (due to strong metallic bonds).
    • Good conductors of heat and electricity (mobile electrons).
    • Exhibit high tensile strength, malleability, and ductility.
    • Similar atomic radii and densities.
    • Generally low ionization energies.

Atomic Radii Trends

  • Effect of Nuclear Charge:
    • As you move from Sc to Zn, the nuclear charge increases, yet atomic radii remain almost constant due to shielding effects by the inner 3d electrons.

Oxidation States

  • Variable Oxidation States:
    • Transition metals often exhibit multiple oxidation states due to the small energy difference between 4s and 3d orbitals.
    • Maximum oxidation state correlates with the number of electrons available in these orbitals for bonding.
    • Example:
    • Fe can exist as Fe$^{2+}$ and Fe$^{3+}$.

Redox Reactions

  • Importance in Transition Metals:
    • Many reactions involving transition metals are redox reactions characterized by changes in oxidation states.