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d & f Block Elements revision notes

Every idea in the d & f Block Elements chapter for JEE Main, with the usual mistakes and the fast methods. Topic 1 is open to everyone; sign in free to read all 26 and download the PDF.

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Transition elements and physical trends

d-block and the transition elements
3× asked, last 2024
(n−1)d1−10ns1−2:3d: Sc to Zn (21 to 30),  4d: Y to Cd (39 to 48),  5d: La, Hf to Hg (57, 72 to 80)(n-1)d^{1-10}ns^{1-2}:\quad \text{3d: Sc to Zn }(21\text{ to }30),\ \ \text{4d: Y to Cd }(39\text{ to }48),\ \ \text{5d: La, Hf to Hg }(57,\ 72\text{ to }80)
Partly filled d in the atom or in any oxidation state (Ag(II): 4d94d^9). Small, highly charged ions with vacant d form complexes.
  • Not every d-block metal is a transition element. Zn, Cd, Hg stay d10d^{10} in atom and ions (soft, diamagnetic compounds; Hg shows +1 and +2). Cu is one: CuX2+\ce{Cu^{2+}} is 3d93d^9. ZZ = 58–71 are f-block.
3d configurations: Cr and Cu exceptions
3× asked, last 2025
Sc 3d14s2, Ti 3d24s2, V 3d34s2, Cr 3d54s1, Mn 3d54s2Fe 3d64s2, Co 3d74s2, Ni 3d84s2, Cu 3d104s1, Zn 3d104s2\begin{gathered}\text{Sc }3d^14s^2,\ \text{Ti }3d^24s^2,\ \text{V }3d^34s^2,\ \textbf{Cr }3d^54s^1,\ \text{Mn }3d^54s^2\\ \text{Fe }3d^64s^2,\ \text{Co }3d^74s^2,\ \text{Ni }3d^84s^2,\ \textbf{Cu }3d^{10}4s^1,\ \text{Zn }3d^{10}4s^2\end{gathered}
Half-filled and full d sets are extra stable (exchange energy). Ions lose 4s4s before 3d3d: FeX2+\ce{Fe^{2+}} is 3d63d^6.
ScTiVCr3d4sMnFeCoNiCu3d4sZn
Cr 3d54s13d^54s^1 and Cu 3d104s13d^{10}4s^1 (red): half-filled and full dd sets win
  • Not 3d44s23d^44s^2 for Cr. It is 3d54s13d^54s^1, so atomic Cr has 6 unpaired electrons (Mn 5, Fe 4, Sc 1). Its valence count, 3d+4s3d+4s, is 6 either way.
Enthalpy of atomisation and melting point
7× asked, last 2025
ΔaH∘: Sc 326, Ti 473, V 515, Cr 397, Mn 281Fe 416, Co 425, Ni 430, Cu 339, Zn 126\begin{gathered}\Delta_aH^\circ:\ \text{Sc }326,\ \text{Ti }473,\ \text{V }515,\ \text{Cr }397,\ \text{Mn }281\\ \text{Fe }416,\ \text{Co }425,\ \text{Ni }430,\ \text{Cu }339,\ \text{Zn }126\end{gathered}
kJ mol⁻¹. Rises with (n−1)d+ns(n-1)d+ns electrons in metal bonding: V peak, Mn dip (d5d^5), Zn lowest. Melting points peak mid-row too.
326Sc473Ti515V397Cr281Mn416Fe425Co430Ni339Cu126ZnΔaH∘\Delta_aH^\circ (kJ mol⁻¹)
Peak at V; dips at Mn (d5d^5) and Zn (only 4s24s^2 in metallic bonding)
  • Melting points dip at the d5d^5 metals Mn and Tc, so Mn < Fe and Tc < Ru. The 5d row has no dip: it peaks at W and then falls, so Re > Os. 4d/5d metals mostly have higher ΔaH\Delta_aH than 3d, but Pd < Ni, Ag < Cu, Zn > Cd > Hg.
  • Not 'full d10d^{10}, strong bonding'. Only ns2ns^2 bonds in Zn, Cd, Hg, so they are soft with the lowest ΔaH\Delta_aH; Hg is a liquid.
Atomic radii and density
1× asked, last 2024
r/pm: Sc 164, Ti 147, V 135, Cr 129, Mn 137, Fe 126, Co 125, Ni 125, Cu 128, Zn 137r/\text{pm}:\ \text{Sc }164,\ \text{Ti }147,\ \text{V }135,\ \text{Cr }129,\ \text{Mn }137,\ \text{Fe }126,\ \text{Co }125,\ \text{Ni }125,\ \text{Cu }128,\ \text{Zn }137
Metallic radii: fall early, then level off (d electrons shield poorly but repel). Density rises: Sc 3.4 to Cu 8.9 g cm⁻³.
rr (pm)ScTiVCrMnFeCoNiCuZn120140160164147135129137126125125128137
Metallic radii fall early, then level off (sheet values)

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22 more concepts in 5 topics

Ionisation enthalpy, oxidation states and E°; Magnetism, colour, catalysis and alloys; Oxides and chromium(VI) compounds; Potassium permanganate; and Lanthanoids and actinoids. Read the first part free. Sign in free with Google to read the rest and download the PDF.

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Ionisation enthalpy, oxidation states and E°

  • Ionisation enthalpies of 3d metals5×
  • Oxidation states across the 3d row7×
  • Higher states: down a group, with O and F11×
  • E°(M²⁺/M) and the Cu⁺/Cu²⁺ case8×
  • E°(M³⁺/M²⁺): oxidants and reductants9×

Magnetism, colour, catalysis and alloys

  • Spin-only magnetic moment29×
  • Colour of 3d ions13×
  • Catalytic behaviour3×
  • Interstitial compounds and alloys3×

Oxides and chromium(VI) compounds

  • Oxides: acidity rises with oxidation state14×
  • K₂Cr₂O₇ from chromite ore4×
  • Chromate–dichromate equilibrium8×
  • Acidified dichromate as an oxidant7×
  • Chromyl chloride and CrO₅5×

Potassium permanganate

  • KMnO₄ from MnO₂9×
  • Manganate and permanganate ions9×
  • KMnO₄ as oxidant: the medium decides11×

Lanthanoids and actinoids

  • Lanthanoid configurations8×
  • Lanthanoid oxidation states15×
  • Lanthanoid contraction
  • Colour, magnetism and uses7×
  • Actinoid configurations and states8×

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