JEE (Main) · Chemistry, Class 12
d- and f-Block Elements: JEE Main PYQ, 2020–2025
d- and f-Block Elements (Chemistry, Class 12) has been asked 155 times in the 111 JEE (Main) shift papers from 2020–2025: about 1.4 questions a paper, 6% of all Chemistry questions. It is the 5th most-asked of 21 Chemistry chapters. The 2025 shifts had 21 from it in all. Last checked 28 October 2026.
Questions per year, all shifts
Year by year.
| Year | Questions |
|---|---|
| 2020 | 11in 14 papers |
| 2021 | 42in 26 papers |
| 2022 | 34in 24 papers |
| 2023 | 10in 12 papers |
| 2024 | 37in 18 papers |
| 2025 | 21in 17 papers |
JEE (Main) is sat in many shifts a year, each with its own paper; the counts add up every shift. 2021–2024 papers had 30 questions a subject, the others 25.
Inside the chapter
Topics asked most.
- Transition element properties77
- Potassium dichromate and permanganate45
- Lanthanoids and actinoids33
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10 d- and f-Block Elements questions to practise.
Our own questions, written in the JEE Main pattern and checked, each with an explanation. Pick an option to see the answer.
Q1 · Chemistry · d- and f-Block Elements
Which of the following first-row transition metals shows the greatest number of oxidation states?
Answer: (B)
The greatest number of oxidation states occurs in or near the middle of the series. Manganese exhibits all the oxidation states from +2 to +7, the most in the first row.
Q2 · Chemistry · d- and f-Block Elements
In the laboratory preparation of KMnO₄, green K₂MnO₄ in alkaline solution is oxidised electrolytically at the anode to purple permanganate. What charge is needed to convert 0.10 mol of manganate completely to permanganate at 100% current efficiency? (F = 96500 C mol⁻¹)
Answer: (A)
At the anode, MnO₄²⁻ → MnO₄⁻ + e⁻. Manganese goes from +6 to +7, so n = 1. Charge = n × moles × F = 1 × 0.10 × 96500 = 9650 C.
Q3 · Chemistry · d- and f-Block Elements
Manganese reaches its group oxidation state of +7 in Mn₂O₇ and in MnO₄⁻. With fluorine, however, the highest binary fluoride of manganese is MnF₄. Which statement gives the correct reason for this difference?
Answer: (A)
The highest oxidation states of transition metals are found in their oxides and fluorides, but oxygen stabilises higher states than fluorine does. For manganese, the highest fluoride is MnF₄ whereas the oxide is Mn₂O₇ (Mn +7) and the oxoanion is MnO₄⁻. The reason is that oxygen can form multiple bonds (M=O) using its lone pairs and the metal's d orbitals, but fluorine can form only single M–F bonds. Fluorine is more electronegative and F₂ is the stronger oxidant than O₂, so options based on electronegativity or oxidising power are factually wrong. Ionisation enthalpies depend on the metal alone, not on the ligand.
Q4 · Chemistry · d- and f-Block Elements
In acidic medium, how many electrons are accepted by one dichromate ion, Cr₂O₇²⁻, when it is reduced completely to Cr³⁺ ions?
Answer: (C)
Find the oxidation state change for one chromium atom, then multiply by the number of chromium atoms in the ion. In Cr₂O₇²⁻, the oxygens are −2 each, so the two Cr atoms must total +12, which gives +6 each. In the product Cr³⁺, each Cr is +3. So each Cr gains 3 electrons, and the dichromate ion gains 3 × 2 = 6 electrons in total.
Q5 · Chemistry · d- and f-Block Elements
Which of the following statements about the chemical behaviour of the actinoid metals is correct?
Answer: (D)
Actinoids are electropositive, highly reactive metals, especially in the finely divided state. They react with boiling water to give a mixture of oxide and hydride and combine with most non-metals at moderate temperatures. Dilute HCl attacks all of them, but HNO₃ affects most of them only slightly because a protective oxide film forms. Alkalis have no action on them, so they are not amphoteric like Al or Zn.
Q6 · Chemistry · d- and f-Block Elements
Lanthanoid ions tend to adopt a stable 4f⁷ (half-filled) configuration where possible. Atomic numbers: Ce = 58, Sm = 62, Eu = 63, Gd = 64, Tb = 65. Atomic ground-state configurations: Sm 4f⁶6s², Eu 4f⁷6s², Gd 4f⁷5d¹6s², Tb 4f⁹6s². Which set contains ions that ALL have the 4f⁷ configuration?
Answer: (B)
Principle: ion configuration = atomic configuration minus the 6s (and 5d) electrons first, then 4f electrons. Eu (4f⁷6s²) → Eu²⁺ is 4f⁷. Gd (4f⁷5d¹6s²) → Gd³⁺ is 4f⁷. Tb (4f⁹6s²) → Tb³⁺ is 4f⁸, and removing one more 4f electron gives Tb⁴⁺ as 4f⁷. Only Eu²⁺, Gd³⁺ and Tb⁴⁺ are all 4f⁷. The other sets include Tb³⁺ (4f⁸), Eu³⁺ (4f⁶) or Sm³⁺ (4f⁵).
Q7 · Chemistry · d- and f-Block Elements
Transition metals of the first series readily form alloys with one another. The main reason is that the atoms of these metals have:
Answer: (A)
Alloys form when atoms of different metals can occupy each other's sites in a common lattice. This is easiest when the atomic radii are close. The first-row transition metals have similar sizes, so they form substitutional alloys such as steel (Fe with C and other metals) and brass-type systems. The key idea is size compatibility in the lattice, not electronic or magnetic similarity.
Q8 · Chemistry · d- and f-Block Elements
The equivalent mass of KMnO₄ (molar mass 158 g mol⁻¹) depends on the medium in which it acts as an oxidant. What are its equivalent masses in strongly acidic solution (MnO₄⁻ → Mn²⁺) and in neutral solution (MnO₄⁻ → MnO₂), respectively?
Answer: (A)
Equivalent mass = molar mass / number of electrons gained per formula unit. In acid, MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O, so n = 5 and the equivalent mass is 158/5 = 31.6. In neutral solution, MnO₄⁻ + 2H₂O + 3e⁻ → MnO₂ + 4OH⁻, so n = 3 and the equivalent mass is 158/3 ≈ 52.7.
Q9 · Chemistry · d- and f-Block Elements
Many Ln³⁺ ions are coloured in aqueous solution because of f–f transitions, and ions whose 4f configurations have the same number of unpaired electrons have similar colours. Atomic numbers: Pr = 59, Nd = 60, Sm = 62, Eu = 63, Gd = 64, Tb = 65, Ho = 67, Tm = 69. Which pair of Ln³⁺ ions is expected to have similar colours?
Answer: (A)
First write the Ln³⁺ configurations. Each Ln³⁺ loses its 6s and 5d/4f electrons to leave 4fⁿ, with n = Z − 57 + 1 − ... which is easiest as n = Z − 57. Pr³⁺ is 4f², Nd³⁺ 4f³, Sm³⁺ 4f⁵, Eu³⁺ 4f⁶, Gd³⁺ 4f⁷, Tb³⁺ 4f⁸, Ho³⁺ 4f¹⁰ and Tm³⁺ 4f¹². Then count unpaired electrons using Hund's rule. In the first half (n ≤ 7) the number of unpaired electrons is n. In the second half (n > 7) it is 14 − n. This gives Pr³⁺ 2, Nd³⁺ 3, Sm³⁺ 5, Eu³⁺ 6, Gd³⁺ 7, Tb³⁺ 6, Ho³⁺ 4 and Tm³⁺ 2. Only Pr³⁺ and Tm³⁺ have equal numbers (2 each), so they are similar in colour; NCERT records both as green. In general, ions with 4fⁿ and 4f¹⁴⁻ⁿ configurations show similar colours.
Q10 · Chemistry · d- and f-Block Elements
On strong heating, potassium permanganate decomposes as 2KMnO₄ → K₂MnO₄ + MnO₂ + O₂. What volume of oxygen, measured at STP, is given by 31.6 g of KMnO₄? (Molar mass of KMnO₄ = 158 g mol⁻¹; molar volume at STP = 22.4 L mol⁻¹)
Answer: (D)
Moles of KMnO₄ = 31.6/158 = 0.20 mol. Two moles of KMnO₄ give one mole of O₂, so 0.10 mol of O₂ is formed, and its volume at STP is 0.10 × 22.4 = 2.24 L.
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All 155 real JEE Main questions from d- and f-Block Elements.
The questions from the actual papers, with the official answer and an explanation for each — chapter by chapter, or as full timed papers.
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About d- and f-Block Elements in JEE Main.
How many questions come from d- and f-Block Elements in JEE Main?
d- and f-Block Elements (Chemistry, Class 12) has been asked 155 times in the 111 JEE (Main) shift papers from 2020–2025: about 1.4 questions a paper, 6% of all Chemistry questions. It is the 5th most-asked of 21 Chemistry chapters. The 2025 shifts had 21 from it in all.
Which topics of d- and f-Block Elements are asked most in JEE Main?
Transition element properties (77), Potassium dichromate and permanganate (45), Lanthanoids and actinoids (33), counted over the papers from 2020–2025.
Is d- and f-Block Elements important for JEE Main 2027?
It is in the syllabus in force, so it can be asked. By past papers it ranks 5 of 21 in Chemistry; use that to decide how much time it gets, not whether to study it.
Where can I solve d- and f-Block Elements JEE Main previous year questions?
On Nikaalle, free: sign up and practise every past JEE Main question from d- and f-Block Elements with an explanation for each, or sit the full papers timed. The ten questions on this page are our own, written in the same pattern.
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