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d- and f-Block Elements in General Chemistry

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  • What defines a transition metal according to IUPAC?
    A transition metal has an incomplete d subshell in its neutral atom or ions. Zn, Cd, and Hg with full d10 configurations are not considered transition metals.
  • What are the four series of transition metals?
    3d series (Sc to Zn), 4d series (Y to Cd), 5d series (La and Hf to Hg), and 6d series (Ac and Rf to Cn).
  • Why do Cr and Cu have unusual electronic configurations?
    Due to small energy difference between (n-1)d and ns orbitals, Cr is 3d5 4s1 and Cu is 3d10 4s1 for extra stability of half-filled or filled d orbitals.
  • What are the general physical properties of transition metals?
    High tensile strength, ductility, malleability, high thermal and electrical conductivity, metallic lustre, high melting and boiling points.
  • What causes the high melting points of transition metals?
    Strong interatomic metallic bonding involving (n-1)d and ns electrons, with maxima at about d5 configuration.
  • What is lanthanoid contraction?
    The gradual decrease in atomic and ionic radii of lanthanoids due to poor shielding by 4f electrons, causing similar radii in 4d and 5d series.
  • How does atomic and ionic size vary across a transition series?
    Atomic and ionic radii decrease slightly with increasing atomic number due to increasing nuclear charge and poor shielding by d electrons.
  • Why do transition metals exhibit multiple oxidation states?
    Because of incomplete filling of d orbitals, allowing loss or sharing of different numbers of d and s electrons.
  • Which first-row transition metal exhibits the greatest number of oxidation states?
    Manganese, showing oxidation states from +2 to +7.
  • Why are Zn, Cd, and Hg not considered transition metals?
    They have completely filled d10 configurations in ground and common oxidation states.
  • What is the general trend in ionisation enthalpies across the first transition series?
    Ionisation enthalpies increase slightly due to increasing nuclear charge but with irregularities from stable d0, d5, and d10 configurations.
  • What causes the irregularities in ionisation enthalpy trends in transition metals?
    Stability of half-filled and fully filled d orbitals and changes in relative energies of 4s and 3d orbitals upon electron removal.
  • How is the magnetic moment of transition metal ions calculated?
    Using the spin-only formula: µ = √(n(n+2)) BM, where n is the number of unpaired electrons.
  • Why do transition metal compounds often show color?
    Due to d-d electronic transitions where electrons absorb visible light to move between split d orbitals influenced by ligands.
  • What are interstitial compounds?
    Compounds formed when small atoms like H, C, or N occupy spaces in metal lattices, e.g., TiC, Fe3H.
  • What is the significance of the lanthanoid contraction on chemical properties?
    It causes elements in the 4d and 5d series to have similar sizes and chemical properties, complicating their separation.
  • How are potassium dichromate and potassium permanganate prepared?
    Dichromate from fusion of chromite ore with alkali and acidification; permanganate from fusion of MnO2 with alkali and oxidation.
  • What is the role of potassium permanganate in redox reactions?
    It acts as a strong oxidizing agent, especially in acidic medium, oxidizing iodides, iron(II), oxalates, and sulphites.
  • What are the main oxidation states of lanthanoids?
    Primarily +3, with some elements showing +2 and +4 states due to extra stability of empty, half-filled, or filled f subshells.
  • How do actinoids differ from lanthanoids in electronic configuration and chemistry?
    Actinoids have variable 5f and 6d occupancy, show more oxidation states, and their 5f electrons participate more in bonding; they are also radioactive.