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Chemistry · Ch 4 — The d- and f-Block Elements

Summary

Summary

  • Electronic configuration: General valence shell configuration for d-block is (n−1)d1−10ns1−2(n-1)d^{1-10} ns^{1-2}; for f-block, it is (n−2)f1−14(n−1)d0−1ns2(n-2)f^{1-14}(n-1)d^{0-1}ns^2.
  • Transition elements: d-block elements (groups 3–12) are called transition elements because they form a transition between s- and p-block; Zn, Cd, Hg are not true transition metals (full d10^{10}).
  • Physical properties: High melting/boiling points, metallic lustre, good conductors, and variable oxidation states (e.g., Mn shows +2 to +7).
  • Variable oxidation states: Due to small energy difference between (n−1)d(n-1)d and nsns orbitals; stability of higher states increases down a group (e.g., Cr3+^{3+} > Cr6+^{6+}).
  • Colour: Most transition metal ions are coloured in aqueous solution due to d–d transitions (splitting of d orbitals in crystal field); e.g., TiX3+\ce{Ti^{3+}} (violet), CuX2+\ce{Cu^{2+}} (blue).
  • Magnetic properties: Unpaired electrons give paramagnetism; CuX2+\ce{Cu^{2+}} (1 unpaired) is paramagnetic, ZnX2+\ce{Zn^{2+}} (d10^{10}) is diamagnetic.
  • Catalytic activity: Many transition metals and their compounds act as catalysts (e.g., Fe in Haber process, V2_2O5_5 in Contact process).
  • Formation of complexes: Due to small size, high charge, and vacant d orbitals; e.g., [Fe(CN)X6]X3−\ce{[Fe(CN)6]^{3-}}, [Cu(NHX3)X4]X2+\ce{[Cu(NH3)4]^{2+}}.
  • Lanthanoids: Elements 58–71 (Ce to Lu); common oxidation state +3; show lanthanoid contraction — steady decrease in atomic/ionic radii due to poor shielding of 4f electrons. …
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