The d- and f-Block Elements

NCERT Class 12 Chemistry Chapter 4

The d- and f-Block Elements for Class 12 Chemistry, JEE and NEET: trends in the transition metals, K₂Cr₂O₇ and KMnO₄, lanthanoids and actinoids.

9 topics Updated 8 Nov 2026

For: Class 12, JEE and NEET, unless a topic says otherwise

In the syllabus: JEE Class 12 syllabus, NEET Class 12 syllabus

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NCERT Chemistry Part I (Class 12), Chapter 4 “The d- and f-Block Elements”, reprint 2026-27.

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Checked on 19 Oct 2026.

Learn in this order

Position of the d-block in the periodic table
Groups 3–12, the 3d, 4d, 5d and 6d series, why they are called transition elements, and the f-block below.

NCERT Section 4.1 10 min read 4 solved examples 8 practice questions
Electronic configurations of the d-block elements
(n − 1)d^¹⁻¹⁰ ns^¹⁻², the chromium and copper exceptions, ions, and Zn, Cd and Hg.

NCERT Section 4.2 14 min read 4 solved examples 8 practice questions
Occurrence of transition elements
How transition metals occur, native metals, and the metal in each pure ore.

JEE and NEET only 10 min read 4 solved examples 8 practice questions
General properties of the transition elements
Radii, ionisation enthalpy, oxidation states, E⊖, magnetic moment, colour, catalysis.

NCERT Section 4.3 33 min read 5 solved examples 9 practice questions
Important compounds of transition elements
Preparation from ores, structures, reactions in acid and alkali, and uses.

NCERT Section 4.4 18 min read 4 solved examples 8 practice questions
Experiment: oxalic acid and Mohr’s salt against KMnO₄
Permanganate as its own indicator, oxalic acid at 333 K, Mohr’s salt unheated, the a_₁M_₁V_₁ = a_₂M_₂V_₂ rule and precautions.

JEE and NEET only 14 min read 3 solved examples 7 practice questions
The lanthanoids
4f configurations, the lanthanoid contraction, its cause and consequences, oxidation states and magnetism.

NCERT Section 4.5 16 min read 3 solved examples 8 practice questions
The actinoids
5f configurations, the actinoid contraction, oxidation states from +3 to +7, and a comparison with lanthanoids.

NCERT Section 4.6 14 min read 3 solved examples 7 practice questions
Applications of d- and f-block elements
Iron and steels, TiO_₂ pigment, MnO_₂ in dry cells, coinage metals, AgBr and catalysts such as V_₂O_₅.

Class 12 only NCERT Section 4.7 9 min read 3 solved examples 6 practice questions

Key formulas in this chapter

Position in the periodic table

d-block: groups 3–12, periods 4–7
Series: 3d Sc–Zn, 4d Y–Cd, 5d La and Hf–Hg, 6d Ac and Rf–Cn
Period number = d shell number + 1
Group number = (n − 1)d electrons + ns electrons
f-block: 4f Ce–Lu (lanthanoids), 5f Th–Lr (actinoids)

Electronic configurations

General: (n − 1)d^¹⁻¹⁰ ns^¹⁻² (Pd: 4d^¹⁰ 5s^⁰)
Cr: [Ar] 3d^⁵ 4s^¹; Cu: [Ar] 3d^¹⁰ 4s^¹
Zn, Cd, Hg, Cn: (n − 1)d^¹⁰ ns^²
Ions lose ns electrons first: Fe^²⁺ = [Ar] 3d^⁶
For usual 3d-series ions with no 4s electrons and intact [Ar] core: d count = Z − 18 − charge

Occurrence

Iron: magnetite Fe_₃O_₄, haematite Fe_₂O_₃, siderite FeCO_₃
Copper: chalcopyrite CuFeS_₂, Cu_₂S, malachite Cu_₂CO_₃(OH)_₂
Chromium: chromite FeCr_₂O_₄; manganese: pyrolusite MnO_₂
Roasting: 2ZnS + 3O_₂ → 2ZnO + 2SO_₂
Calcination: ZnCO_₃ → ZnO + CO_₂
Mass % of metal = (mass of metal in one mole of compound ÷ molar mass of compound) × 100

General properties

Spin-only magnetic moment: μ = √(n(n + 2)) BM
One unpaired electron: μ = 1.73 BM
Highest stable state up to Mn = number of 4s + 3d electrons
Standard oxidising power in acid: VO_₂^⁺ < Cr_₂O_₇^²⁻ < MnO_₄^⁻
2Cu^⁺ → Cu^²⁺ + Cu
3MnO_₄^²⁻ + 4H^⁺ → 2MnO_₄^⁻ + MnO_₂ + 2H_₂O

Important compounds

4FeCr_₂O_₄ + 8Na_₂CO_₃ + 7O_₂ → 8Na_₂CrO_₄ + 2Fe_₂O_₃ + 8CO_₂
2CrO_₄^²⁻ + 2H^⁺ ⇌ Cr_₂O_₇^²⁻ + H_₂O
Cr_₂O_₇^²⁻ + 14H^⁺ + 6e^⁻ → 2Cr^³⁺ + 7H_₂O (E⊖ = 1.33 V)
2MnO_₂ + 4KOH + O_₂ → 2K_₂MnO_₄ + 2H_₂O
3MnO_₄^²⁻ + 4H^⁺ → 2MnO_₄^⁻ + MnO_₂ + 2H_₂O
MnO_₄^⁻ + 8H^⁺ + 5e^⁻ → Mn^²⁺ + 4H_₂O (E⊖ = 1.52 V)
MnO_₄^⁻ + 4H^⁺ + 3e^⁻ → MnO_₂ + 2H_₂O (E⊖ = 1.69 V)
2KMnO_₄ → K_₂MnO_₄ + MnO_₂ + O_₂ (at 513 K)

Experiment: KMnO₄ titrations

MnO_₄^⁻ + 8H^⁺ + 5e^⁻ → Mn^²⁺ + 4H_₂O
2MnO_₄^⁻ + 5C_₂O_₄^²⁻ + 16H^⁺ → 2Mn^²⁺ + 10CO_₂ + 8H_₂O
MnO_₄^⁻ + 5Fe^²⁺ + 8H^⁺ → Mn^²⁺ + 5Fe^³⁺ + 4H_₂O
a_₁M_₁V_₁ = a_₂M_₂V_₂
Strength (g/L) = molarity × molar mass

Lanthanoids

Lanthanoids: Ce (Z = 58) to Lu (Z = 71)
Ln^³⁺: 4f^ⁿ, n = 1 to 14
E⊖(Ce^⁴⁺/Ce^³⁺) = +1.74 V
E⊖(Ln^³⁺/Ln) = −2.2 to −2.4 V (Eu −2.0 V)
Spin-only moment: μ = √(n(n + 2)) BM

Actinoids

Actinoids: Th (Z = 90) to Lr (Z = 103)
Typical configurations: [Rn] 5f^¹⁻¹⁴ 6d^⁰⁻¹ 7s^²; Th 6d^² 7s^²; Lr 5f^¹⁴ 6d^¹ 7s^² (NCERT; modern 7p^¹)
Highest states: Th +4, Pa +5, U +6, Np +7
Am: [Rn] 5f^⁷ 7s^²; Cm: [Rn] 5f^⁷ 6d^¹ 7s^²

Applications

Contact process catalyst: V_₂O_₅ (V +5)
Haber process catalyst: Fe
Ziegler catalyst: TiCl_₄ + Al(CH_₃)_₃
Wacker process: ethene → ethanal, PdCl_₂
Hydrogenation of fats: Ni

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Key formulas in this chapter

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