Chapter 4 · Chemistry
The d- and f-Block Elements: Chapter Introduction
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Iron bridges, copper wires and bright blue, purple and orange solutions all come from one part of the periodic table. The d-block (groups 3–12) fills d orbitals; the f-block (two rows below) fills f orbitals. Variable oxidation states, colour, magnetism and catalysis make them special.
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Zinc Is in the d-Block, So Why Is It Not a Transition Metal?A transition element has an incompletely filled d subshell in its atom or in a common ion. Iron (3d⁶) passes; copper (3d¹⁰ atom) passes through Cu²⁺ (3d⁹); zinc stays 3d¹⁰ even as Zn²⁺, so Zn, Cd and Hg are d-block but not transition metals.Chemistry
Key points
- d-block: the middle of the periodic table, groups 3–12; electrons fill the d orbitals (5 orbitals, up to 10 electrons).
- f-block: two separate rows at the bottom, the lanthanoids (4f) and actinoids (5f); electrons fill the f orbitals (7 orbitals, up to 14 electrons).
- Transition metals show variable oxidation states, form coloured compounds, are often paramagnetic and are good catalysts.
- Everyday examples: iron (steel, bridges), copper (wires), blue CuSO₄, purple KMnO₄, orange K₂Cr₂O₇.
Where the d- and f-blocks sit
| Block | Position | Orbitals filling | Series |
|---|---|---|---|
| d-block | groups 3–12 (middle) | (n−1)d | 3d, 4d, 5d, 6d |
| f-block | two rows at the bottom | (n−2)f | 4f lanthanoids, 5f actinoids |
The f-block is drawn separately so that the table stays compact: each f series has 14 elements.
Why they are special
- Variable oxidation states: manganese shows every state from +2 to +7.
- Coloured compounds: most transition-metal ions are coloured.
- Magnetism: many ions have unpaired electrons and are paramagnetic.
- Catalysts: iron in the Haber process, V₂O₅ in the contact process, nickel in hydrogenation.
- They also form complexes and alloys and have high melting points.
What this chapter covers
- Electronic configurations (and the Cr, Cu exceptions)
- General properties: size, ionisation enthalpy, oxidation states, E°, magnetism, colour, complexes, catalysis, interstitial compounds, alloys
- Two key compounds: K₂Cr₂O₇ and KMnO₄
- The lanthanoids (lanthanoid contraction) and the actinoids
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More from The d- and f-Block Elements
d-Block Configurations: Why Chromium and Copper Break the RuleThe d-block's general configuration is (n−1)d¹⁻¹⁰ ns¹⁻², with 4s filling before 3d. Chromium (3d⁵4s¹) and copper (3d¹⁰4s¹) move one 4s electron into 3d, because 3d and 4s are very close in energy and half-filled and full d sets are extra stable.Chemistry
Why Transition Metals Have High Melting PointsIn transition metals the (n−1)d electrons join the ns electrons in metallic bonding, so the bonds are strong and the metals are hard with high melting points. Across the 3d series melting points peak near the middle (Mn is an exception) and fall to zinc (d¹⁰).Chemistry
Five More Protons, Same Size: Radius and Ionisation Enthalpy across the 3d SeriesAcross the 3d series each new electron enters the inner (n−1)d subshell and shields the outer 4s electrons, nearly cancelling the extra nuclear charge. So atomic radii change only slightly and the first ionisation enthalpy rises slowly (631 → 906 kJ/mol), unlike across a normal period.Chemistry
One Element, Six Oxidation States: Why Transition Metals VaryThe ns and (n−1)d electrons of a transition metal are close in energy, so both can take part in bonding. Manganese (3d⁵ 4s²) shows every state from +2 to +7; the most states occur in the middle of the series, Sc shows only +3 and Zn only +2, and the states change in steps of one.Chemistry
Zinc Fizzes, Copper Stays Silent: Electrode Potentials of the 3d MetalsCopper is the only 3d metal with a positive E°(M²⁺/M) (+0.34 V), so it gives no H₂ with dilute acids. Turning Cu(s) into Cu²⁺(aq) costs more (atomisation + two ionisations) than hydration pays back: 921 against zinc's 711 kJ/mol. Stable d⁵ and d¹⁰ bend the trend: Mn and Zn dip, Mn³⁺ is a strong oxidant, Fe³⁺ is stable.Chemistry