Class 12 Chemistry MCQ Chapter 4 The d-and f-Block Elements

Published On: June 5, 2026

Class 12 Chemistry MCQ Chapter 4 The d- and f-Block Elements

Are you looking for AHSEC Class 12 Chemistry MCQ Chapter 4 The d-and f-Block Elements English Medium? If yes, then you have come to the right place. This article provides a complete collection of Multiple Choice Questions (MCQs) with accurate answers and detailed explanations from Chapter 4: The d-and f-Block Elements for AHSEC Higher Secondary students.

These MCQ solutions are prepared according to the latest AHSEC syllabus and examination pattern. The questions cover all important topics of the chapter, including transition elements, inner transition elements, electronic configurations, oxidation states, magnetic properties, lanthanides, actinides, lanthanoid contraction, and the chemical properties of d- and f-block elements. Regular practice of these objective questions will help students strengthen their conceptual understanding and improve their examination performance.

All questions and answers are written in simple and easy-to-understand English, making them ideal for quick revision and effective exam preparation. Whether you are preparing for unit tests, school examinations, competitive exams, or the AHSEC Higher Secondary Final Examination, these MCQ solutions will help you build confidence and score better marks.

Practice these Chapter 4 MCQs regularly to improve your understanding of important concepts and perform well in your Chemistry examinations.

Part I

The d- and f-Block Elements

VSA & MCQ

I. Short Question-Answer

Q. What are d-block elements?

Ans: Elements in which the last electron enters the (n−1)d subshell.

Q. What are f-block elements?

Ans: Elements in which the last electron enters the (n−2)f subshell.

Q. What are transition elements?

Ans: Elements having partially filled d-orbitals in ground or excited state.

Q. Why Zn, Cd, Hg are not transition elements?

Ans: They have completely filled d¹⁰ configuration.

Q. What is general electronic configuration of d-block elements?

Ans: (n−1)d¹–¹⁰ ns¹–²

Q. What are lanthanoids?

Ans: Elements from La to Lu with filling of 4f orbitals.

Q. What are actinoids?

Ans: Elements from Ac to Lr with filling of 5f orbitals.

Q. What is lanthanoid contraction?

Ans: Gradual decrease in atomic size across lanthanoids.

Q. Cause of lanthanoid contraction?

Ans: Poor shielding of 4f electrons.

Q. What is oxidation state?

Ans: Charge on an atom in a compound.

Q. Why transition metals show variable oxidation states?

Ans: Due to similar energies of ns and (n−1)d orbitals.

Q. Why transition metals form coloured compounds?

Ans: Due to d–d electronic transitions.

Q. What is paramagnetism?

Ans: Attraction due to presence of unpaired electrons.

Q. Formula for magnetic moment?

Ans: μ = √[n(n+2)] BM

Q. What is complex formation?

Ans: Formation of coordination compounds with ligands.

Q. What is catalytic property of transition metals?

Ans: Ability to change rate of reaction.

Q. What is interstitial compound?

Ans: Compound formed when small atoms occupy interstitial spaces.

Q. What are alloys?

Ans: Homogeneous mixtures of metals.

Q. Why transition metals have high melting points?

Ans: Due to strong metallic bonding.

Q. What is disproportionation reaction?

Ans: Same element undergoes oxidation and reduction.

Q. Example of disproportionation.

Ans: 2Cu⁺ → Cu²⁺ + Cu

Q. What is +3 oxidation state common for lanthanoids?

Ans: Stable due to removal of three electrons.

Q. What is actinoid contraction?

Ans: Decrease in atomic size across actinoids.

Q. Why actinoids are radioactive?

Ans: Due to unstable nuclei.

Q. What is shielding effect?

Ans: Reduction in nuclear attraction by inner electrons.

Q. What is effective nuclear charge?

Ans: Net positive charge experienced by valence electrons.

Q. What is crystal field splitting?

Ans: Splitting of d-orbitals in a ligand field.

Q. What is high spin complex?

Ans: Complex with maximum unpaired electrons.

Q. What is low spin complex?

Ans: Complex with paired electrons.

Q. What is coordination number?

Ans: Number of ligands attached to metal ion.

II. Multiple Choice Questions (MCQs)

Q. d-block elements are present in:

(a) s-block

(b) p-block

(d) f-block

Ans: (c)

Q. f-block elements are called:

(a) Transition

(b) Inner transition

(d) Halogens

Ans: (b)

Q. Zn is not a transition element because:

(a) High energy

(b) Filled d-orbital

(d) Low melting point

Ans: (b)

Q. Variable oxidation states due to:

(a) Same orbitals

(b) ns and d energy similarity

(d) Low energy

Ans: (b)

Q. Colour of compounds due to:

(a) s-electrons

(b) p-electrons

(d) f-electrons

Ans: (c)

Q. Magnetic moment depends on:

(a) Protons

(b) Neutrons

(d) Mass

Ans: (c)

Q. Lanthanoid contraction due to:

(a) Strong shielding

(b) Weak shielding

(d) High energy

Ans: (b)

Q. Alloys are:

(a) Compounds

(b) Mixtures

(d) Gases

Ans: (b)

Q. Interstitial compounds have:

(a) Large atoms

(b) Small atoms in spaces

(d) Only gases

Ans: (b)

Q. Catalytic activity due to:

(a) Fixed oxidation state

(b) Variable oxidation states

(d) Low energy

Ans: (b)

Q. Lanthanoids show common oxidation state:

(a) +1

(b) +2

(d) +4

Ans: (c)

Q. Actinoids are:

(a) Stable

(b) Radioactive

(d) Noble

Ans: (b)

Q. Crystal field splitting occurs in:

(a) s-orbitals

(b) p-orbitals

(d) f-orbitals

Ans: (c)

Q. Assertion: Transition metals show variable oxidation states.

Reason: ns and d orbitals have similar energies.

(a) Both true, R correct explanation