Elements of Group 13, 14 and 15 — Class 11 MCQs with Answers
Class 11 CBSE Chemistry · Chapter 304
40 practice questions · 20 Easy · 20 Medium · Updated
Practise the most important Class 11 CBSE Chemistry questions from Chapter 304, "Elements of Group 13, 14 and 15". You get 4 timed quizzes made from 40 NCERT-based MCQs, with answers and explanations. The questions are split into 20 Easy and 20 Medium. 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 "Elements of Group 13, 14 and 15", 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 Elements of Group 13, 14 and 15, then move to Medium to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 11 Chemistry mastery score. 6 sample questions are solved in full below, with the answer and a worked explanation. Sign in free to start practising.
Key concepts: Elements of Group 13, 14 and 15 (Class 11 Chemistry)
This chapter covers the first three families of the p-block: group 13 (ns²np¹, the boron family), group 14 (ns²np², the carbon family) and group 15 (ns²np³, the nitrogen family). In each family the head element — boron, carbon and nitrogen — behaves abnormally because it is small, highly electronegative and has no d orbitals in its valence shell, which caps its covalency at four and pushes it towards pπ-pπ multiple bonding. Below the head element the trends settle down and two new ideas appear: the inert pair effect, which makes the lower oxidation state more stable down group 13 and 14, and the availability of d orbitals, which lets silicon and phosphorus expand their octets. The chapter then works through the important compounds — borax, boric acid, diborane, aluminium compounds, the allotropes of carbon, silica, silicates and silicones, ammonia, nitric acid, the oxides of nitrogen, the allotropes of phosphorus, phosphine, phosphorus halides and the oxoacids of phosphorus.
- Group 13 trends
- Boron is a metalloid while Al, Ga, In and Tl are metals. The group oxidation state is +3, and atomic radius does not rise smoothly — gallium is marginally smaller than aluminium because the poorly shielding 3d electrons added before it raise the effective nuclear charge. Gallium also has an exceptionally low melting point of about 303 K.
- Inert pair effect
- Going down groups 13 and 14, the ns² pair of electrons becomes progressively reluctant to take part in bonding because the intervening d and f electrons shield the nucleus poorly and the s electrons are held more tightly. Hence Tl⁺ is more stable than Tl³⁺ and Pb²⁺ more stable than Pb⁴⁺, which makes Tl³⁺ and Pb⁴⁺ strong oxidising agents.
- Anomalous behaviour of boron
- Boron is far smaller and more electronegative than the rest of its group and its valence shell offers only four orbitals, so its maximum covalency is four. It never forms a simple B³⁺ ion, its trihalides are electron-deficient Lewis acids, and it forms [BF₄]⁻ but never [BF₆]³⁻, unlike aluminium which uses 3d orbitals to give [AlF₆]³⁻.
- Borax
- Borax, Na₂B₄O₇·10H₂O, is the commonest boron mineral and gives an alkaline solution on hydrolysis. Heated strongly it swells, loses its water and finally melts to a clear glassy bead of sodium metaborate and boric anhydride; the B₂O₃ in this bead combines with coloured metal oxides to give the characteristic colours of the borax bead test.
Elements of Group 13, 14 and 15 — important questions & MCQs with answers (Class 11 Chemistry)
6 solved questions from this chapter's difficulty levels, each with its answer and explanation. The other 34 are timed and scored when you sign in.
- Q1Easy
The general valence shell electronic configuration of group 13 elements is
A.ns²np²B.ns²np³C.ns²np¹✓ CorrectD.ns¹Answer: C. ns²np¹
Explanation: The boron family has two electrons in the valence s orbital and one in a p orbital, giving ns²np¹ and a group oxidation state of +3.
- Q2Easy
The formula of borax is
A.Na₂B₄O₇·10H₂O✓ CorrectB.B₂H₆C.NaBO₂D.H₃BO₃Answer: A. Na₂B₄O₇·10H₂O
Explanation: Borax is sodium tetraborate decahydrate; on heating it first swells as it loses water and finally melts to a clear glassy bead.
- Q3Easy
The tendency of an element to link with itself into long chains (catenation) is greatest in
A.siliconB.germaniumC.tinD.carbon✓ CorrectAnswer: D. carbon
Explanation: The C–C bond enthalpy of about 348 kJ mol⁻¹ is far larger than that of Si–Si or Ge–Ge, so catenation falls off sharply on going down group 14.
- Q4Medium
The atomic radius of gallium is slightly smaller than that of aluminium because
A.gallium has a smaller nuclear chargeB.gallium has fewer electron shells than aluminiumC.the poorly shielding 3d electrons in gallium raise the effective nuclear charge✓ CorrectD.gallium is a non-metalAnswer: C. the poorly shielding 3d electrons in gallium raise the effective nuclear charge
Explanation: Gallium comes just after the first transition series; the newly added 3d electrons screen the nucleus poorly, so the outer electrons are pulled in and Ga ends up marginally smaller than Al.
- Q5Medium
Diborane is described as an electron-deficient molecule because
A.it contains no hydrogen atomsB.it has only 12 valence electrons and uses two three-centre two-electron bonds✓ CorrectC.boron carries a formal negative chargeD.it contains a boron-boron triple bondAnswer: B. it has only 12 valence electrons and uses two three-centre two-electron bonds
Explanation: Eight bonded atoms would need at least 16 electrons for ordinary two-centre bonds, but B₂H₆ has only 12, so the two B–H–B bridges are three-centre two-electron 'banana' bonds.
- Q6Medium
CO₂ is a gas whereas SiO₂ is a very high melting solid because
A.CO₂ has the higher molar massB.CO₂ is an ionic compoundC.carbon forms pπ-pπ double bonds giving discrete O=C=O molecules, while SiO₂ is a covalent network✓ CorrectD.SiO₂ is a metal oxideAnswer: C. carbon forms pπ-pπ double bonds giving discrete O=C=O molecules, while SiO₂ is a covalent network
Explanation: Small carbon overlaps sideways with oxygen and completes its octet within one molecule held by weak forces, while silicon is too large for such pπ overlap and instead forms four single Si–O bonds in an extended lattice.
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Start this chapter free →Elements of Group 13, 14 and 15 — FAQs
What are the key concepts in Class 11 Chemistry Elements of Group 13, 14 and 15?+
This chapter covers the first three families of the p-block: group 13 (ns²np¹, the boron family), group 14 (ns²np², the carbon family) and group 15 (ns²np³, the nitrogen family). In each family the head element — boron, carbon and nitrogen — behaves abnormally because it is small, highly electronegative and has no d orbitals in its valence shell, which caps its covalency at four and pushes it towards pπ-pπ multiple bonding. Below the head element the trends settle down and two new ideas appear: the inert pair effect, which makes the lower oxidation state more stable down group 13 and 14, and the availability of d orbitals, which lets silicon and phosphorus expand their octets. The chapter then works through the important compounds — borax, boric acid, diborane, aluminium compounds, the allotropes of carbon, silica, silicates and silicones, ammonia, nitric acid, the oxides of nitrogen, the allotropes of phosphorus, phosphine, phosphorus halides and the oxoacids of phosphorus. Key ideas include Group 13 trends, Inert pair effect, Anomalous behaviour of boron, Borax.
What does Class 11 Chemistry Chapter 304 (Elements of Group 13, 14 and 15) cover on XamBaaz?+
It has 40 NCERT-based MCQs on "Elements of Group 13, 14 and 15": 20 Easy and 20 Medium. Together they make 4 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 "Elements of Group 13, 14 and 15" questions free to practise?+
Yes. Sign in with Google to practise "Elements of Group 13, 14 and 15" free. Full unlimited access is ₹999/year on a launch offer until 1 December 2026. No chapter is charged separately.
How should I revise "Elements of Group 13, 14 and 15" for the exam?+
Start with the Easy quiz to check your basics, then try Medium to practise applying them. There are 4 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 "Elements of Group 13, 14 and 15" MCQs available with answers?+
Yes. 6 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 "Elements of Group 13, 14 and 15" 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 Elements of Group 13, 14 and 15 (Class 11 Chemistry)?+
The questions that matter most test Group 13 trends, Inert pair effect, Anomalous behaviour of boron, Borax. This page shows 6 solved important MCQs with answers and explanations; all 40 questions on the chapter are available as timed quizzes once you sign in.
Is there an online quiz for Elements of Group 13, 14 and 15?+
Yes — Class 11 Chemistry Elements of Group 13, 14 and 15 has timed online quizzes at Easy and Medium levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.