The d- and f-Block Elements — Class 12 MCQs with Answers
Class 12 CBSE Chemistry · Chapter 4
96 practice questions · 32 Easy · 32 Medium · 32 Hard · Updated
Practise the most important Class 12 CBSE Chemistry questions from Chapter 4, "The d- and f-Block Elements". You get 9 timed quizzes made from 96 NCERT-based MCQs, with answers and explanations. The questions are split into 32 Easy, 32 Medium and 32 Hard. Warm up on the basics, then move on to the exam-level questions that set top scorers in CBSE & Maharashtra HSC Board exams, JEE Main, MHT-CET, JEE Advanced and NEET UG apart.
To score well in "The d- and f-Block Elements", focus on reactions, key concepts and careful numericals. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This trains you to stay accurate under time pressure, as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.
Use this chapter for focused revision. Start with the Easy set to check your basics on The d- and f-Block Elements, then move to Medium and Hard to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 12 Chemistry mastery score. 14 sample questions are solved in full below, with the answer and a worked explanation. Sign in free to start practising.
Key concepts: The d- and f-Block Elements (Class 12 Chemistry)
The d- and f-Block Elements covers the transition and inner-transition metals: their (n−1)d ns configurations, variable oxidation states, coloured and paramagnetic ions, catalytic behaviour, alloy and complex formation, the lanthanoid contraction, and the preparation and oxidising action of K₂Cr₂O₇ and KMnO₄.
- Transition (d-block) elements
- Elements with an incompletely filled d-subshell in the atom or a common ion; general configuration (n−1)d¹⁻¹⁰ ns⁰⁻². Groups 3–12 of periods 4–7.
- Variable oxidation states
- The (n−1)d and ns electrons have similar energies, so both take part in bonding, giving a range of states (e.g. Mn shows +2 to +7).
- Atomic and ionic radii trend
- Radii fall across a series then level off due to increasing nuclear charge balanced by d-electron shielding; 4d and 5d elements have nearly equal size.
- Coloured ions
- Colour arises from d–d electronic transitions absorbing visible light; ions with d⁰ or d¹⁰ (Sc³⁺, Zn²⁺) are colourless as no such transition is possible.
The d- and f-Block Elements — important questions & MCQs with answers (Class 12 Chemistry)
14 solved questions from this chapter's difficulty levels, each with its answer and explanation. The other 82 are timed and scored when you sign in.
- Q1Easy
d-block elements have last electron in:
A.d-orbital✓ CorrectB.s-orbitalC.p-orbitalD.f-orbitalAnswer: A. d-orbital
Explanation: The d-block gets its name because the last electron fills an (n−1)d orbital, e.g. Sc = [Ar]3d¹4s² — contrast s-block (last electron in ns) and p-block (np).
- Q2Easy
Lanthanide contraction refers to the:
A.Decrease in 3d seriesB.Sudden expansion of f-orbitalsC.Increase in radii of actinidesD.Steady decrease in atomic and ionic radii across the 4f series✓ CorrectAnswer: D. Steady decrease in atomic and ionic radii across the 4f series
Explanation: Lanthanide contraction is the steady, cumulative decrease in atomic and ionic radii from La to Lu across the 4f series, caused by the poor shielding that 4f electrons provide for each added proton.
- Q3Easy
Most transition metal ions are:
A.Black alwaysB.ColourlessC.Coloured✓ CorrectD.White alwaysAnswer: C. Coloured
Explanation: Partly-filled d-orbitals let electrons absorb visible light via d-d transitions, so most transition-metal ions like Cu²⁺ and Mn²⁺ are coloured — only d⁰ or d¹⁰ ions such as Sc³⁺ or Zn²⁺ stay colourless.
- Q4Easy
The most common oxidation state of lanthanides is:
A.+2B.+4C.+3✓ CorrectD.+5Answer: C. +3
Explanation: +3 is the characteristic and most stable oxidation state across the lanthanide series, arising from loss of the two 6s and one 5d (or 4f) electron to reach a relatively stable configuration.
- Q5Easy
The electronic configuration of Sc (Z = 21) in ground state is:
A.[Ar] 4s² 4p¹B.[Ar] 3d² 4s¹C.[Ar] 3d³D.[Ar] 3d¹ 4s²✓ CorrectAnswer: D. [Ar] 3d¹ 4s²
Explanation: Aufbau fills 4s before 3d, so Sc (Z = 21) is [Ar]3d¹4s² — the last electron enters the 3d, not 4p, orbital, which is why scandium is the first d-block element.
- Q6Easy
Lanthanides have general electronic configuration:
A.[Rn] 5f¹⁻¹⁴ 6d⁰⁻¹ 7s²B.[Xe] 4f¹⁻¹⁴ 5d⁰⁻¹ 6s²✓ CorrectC.[Ar] 3d¹⁻¹⁰ 4s²D.[Kr] 4d¹⁻¹⁰ 5s²Answer: B. [Xe] 4f¹⁻¹⁴ 5d⁰⁻¹ 6s²
Explanation: Lanthanides fill the 4f subshell after the [Xe] core, with electron configuration [Xe]4f¹⁻¹⁴5d⁰⁻¹6s² — the 5d electron appears only for a few members like La, Ce and Gd.
- Q7Medium
Transition metals show:
A.Variable oxidation states✓ CorrectB.Fixed +1 onlyC.Only +2D.NoneAnswer: A. Variable oxidation states
Explanation: Because the (n−1)d and ns electrons lie close in energy, transition metals can lose different numbers of electrons, giving variable oxidation states — e.g. Mn ranges from +2 to +7, unlike the fixed +1 of alkali metals.
- Q8Medium
Lanthanide contraction is the:
A.Sudden jumpB.Increase in sizeC.Steady decrease in size of lanthanide ions across the series✓ CorrectD.No changeAnswer: C. Steady decrease in size of lanthanide ions across the series
Explanation: Lanthanide contraction is the steady, cumulative shrinkage of atomic and ionic radii across La to Lu, caused by the poor shielding of 4f electrons — it is gradual, not a sudden jump or an increase.
- Q9Medium
The spin-only magnetic moment (μB) of Fe²⁺ (3d⁶) is approximately:
A.2.83B.4.90✓ CorrectC.3.87D.5.92Answer: B. 4.90
Explanation: Fe²⁺ (3d⁶) high-spin has 4 unpaired electrons (t₂g⁴eg² pattern), so μ = √(n(n+2)) = √(4×6) = √24 ≈ 4.90 μB — not the 5-unpaired value (5.92) that a d⁵ ion like Mn²⁺ would give.
- Q10Medium
The principal cause of lanthanide contraction is:
A.Poor shielding of 4f electrons✓ CorrectB.Effective shielding by 4f electronsC.Relativistic effect onlyD.Increase in atomic radiusAnswer: A. Poor shielding of 4f electrons
Explanation: 4f electrons shield the nuclear charge poorly because of their diffuse, complex orbital shapes, so effective nuclear charge rises steadily across La to Lu, pulling in the electron cloud at every step.
- Q11Medium
The spin-only magnetic moment of Mn²⁺ (3d⁵) is:
A.5.92 μB✓ CorrectB.3.87 μBC.4.90 μBD.1.73 μBAnswer: A. 5.92 μB
Explanation: Mn²⁺ (3d⁵) has all 5 d-electrons unpaired (half-filled, high-spin), so μ = √(5×7) = √35 ≈ 5.92 μB — the highest spin-only value possible for a first-row transition ion.
- Q12Hard
Why are many transition metals good catalysts?
A.Coloured ionsB.Low densityC.Soft textureD.Variable oxidation states + ability to adsorb reactants✓ CorrectAnswer: D. Variable oxidation states + ability to adsorb reactants
Explanation: Transition metals catalyse reactions because their variable oxidation states let them form unstable intermediates, and their surfaces adsorb reactants, weakening bonds — colour and low density play no role in catalysis.
- Q13Hard
All actinides are:
A.StableB.Radioactive✓ CorrectC.LiquidD.GaseousAnswer: B. Radioactive
Explanation: Every actinide, from thorium and uranium through synthetic transuranics like plutonium, has an unstable nucleus, so the entire series is radioactive.
- Q14Hard
In the industrial preparation of KMnO₄, K₂MnO₄ is converted to KMnO₄ by:
A.Electrolytic oxidation in alkaline solution✓ CorrectB.Reduction with H₂C.Heating with KClD.Treatment with HClAnswer: A. Electrolytic oxidation in alkaline solution
Explanation: K₂MnO₄ (Mn⁶⁺, green) is converted to KMnO₄ (Mn⁷⁺, purple) by electrolytic oxidation in alkaline solution at the anode, or by disproportionation with acid: 3MnO₄²⁻ + 4H⁺ → 2MnO₄⁻ + MnO₂ + 2H₂O.
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Start this chapter free →The d- and f-Block Elements — FAQs
What are the key concepts in Class 12 Chemistry The d- and f-Block Elements?+
The d- and f-Block Elements covers the transition and inner-transition metals: their (n−1)d ns configurations, variable oxidation states, coloured and paramagnetic ions, catalytic behaviour, alloy and complex formation, the lanthanoid contraction, and the preparation and oxidising action of K₂Cr₂O₇ and KMnO₄. Key ideas include Transition (d-block) elements, Variable oxidation states, Atomic and ionic radii trend, Coloured ions.
What does Class 12 Chemistry Chapter 4 (The d- and f-Block Elements) cover on XamBaaz?+
It has 96 NCERT-based MCQs on "The d- and f-Block Elements": 32 Easy, 32 Medium and 32 Hard. Together they make 9 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE & Maharashtra HSC Board exams, JEE Main, MHT-CET, JEE Advanced and NEET UG.
Are these "The d- and f-Block Elements" questions free to practise?+
Yes. Sign in with Google to practise "The d- and f-Block Elements" free. Full unlimited access is ₹999/year on a launch offer until 1 December 2026. No chapter is charged separately.
How should I revise "The d- and f-Block Elements" for the exam?+
Start with the Easy quiz to check your basics, then try Medium and Hard to practise applying them. There are 9 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.
Are these "The d- and f-Block Elements" MCQs available with answers?+
Yes. 14 sample questions are shown here in full, each with the correct option and a step-by-step "Why" explanation. Sign in free with Google to start practising, with instant scoring.
Is there negative marking in the "The d- and f-Block Elements" quizzes?+
Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip, the same negative marking as JEE Main, JEE Advanced and NEET UG. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.
What are the important questions from The d- and f-Block Elements (Class 12 Chemistry)?+
The questions that matter most test Transition (d-block) elements, Variable oxidation states, Atomic and ionic radii trend, Coloured ions. This page shows 14 solved important MCQs with answers and explanations; all 96 questions on the chapter are available as timed quizzes once you sign in.
Is there an online quiz for The d- and f-Block Elements?+
Yes — Class 12 Chemistry The d- and f-Block Elements has timed online quizzes at Easy, Medium and Hard levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.