Nuclear Chemistry and Radioactivity — Class 11 MCQs with Answers
Class 11 CBSE Chemistry · Chapter 307
40 practice questions · 20 Easy · 20 Medium · Updated
Practise the most important Class 11 CBSE Chemistry questions from Chapter 307, "Nuclear Chemistry and Radioactivity". 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 "Nuclear Chemistry and Radioactivity", 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 Nuclear Chemistry and Radioactivity, 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: Nuclear Chemistry and Radioactivity (Class 11 Chemistry)
Ordinary chemistry rearranges electrons; nuclear chemistry changes the nucleus itself. Beginning with Becquerel's accidental discovery in 1896 that uranium salts fog a wrapped photographic plate, this chapter looks at the three natural radiations α, β and γ and how they differ in charge, mass, ionising power and penetrating power. It then explains why some nuclei are unstable in terms of the neutron-to-proton ratio and the band of stability, works through the decay modes (α, β⁻, β⁺ and electron capture) and the group displacement law, treats decay as a first order rate process with a decay constant, half-life and average life, and finally covers artificial transmutation, fission, fusion, mass defect and binding energy, nuclear reactors and the everyday uses of radioisotopes in dating, medicine and agriculture.
- Radioactivity
- The spontaneous emission of α, β or γ radiation by an unstable nucleus. It was discovered by Henri Becquerel in 1896 with uranium salts, and Marie and Pierre Curie then isolated polonium and radium from pitchblende. The rate is unaffected by temperature, pressure or chemical combination.
- Alpha, beta and gamma radiation
- An α-particle is a helium nucleus ⁴₂He²⁺, a β-particle is a fast electron ⁰₋₁e, and a γ-ray is a high energy photon with no charge and no rest mass. Ionising power falls α > β > γ while penetrating power rises in the reverse order α < β < γ; α is stopped by paper, β by thin aluminium and γ needs thick lead.
- n/p ratio and the band of stability
- Plotting neutrons against protons for stable nuclides gives a narrow band. Light stable nuclei have n/p about 1, and the ratio rises to roughly 1.5 near the heavy end. Nuclides outside the band are radioactive and every nuclide with atomic number greater than 83 is unstable.
- Modes of decay
- A nucleus above the band (too many neutrons) emits a β⁻ particle, turning a neutron into a proton. A nucleus below the band (too many protons) emits a positron or captures a K-shell electron, turning a proton into a neutron. Very heavy nuclides shed mass by α emission, and γ emission simply removes excess energy.
Nuclear Chemistry and Radioactivity — 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
Radioactivity was discovered in 1896 while studying the behaviour of uranium salts by
A.Marie CurieB.Henri Becquerel✓ CorrectC.Ernest RutherfordD.James ChadwickAnswer: B. Henri Becquerel
Explanation: Henri Becquerel found that a potassium uranyl sulphate salt fogged a wrapped photographic plate on its own, which showed that uranium emits penetrating radiation spontaneously.
- Q2Easy
When a nucleus emits one α-particle, its mass number and atomic number change by
A.mass number decreases by 4, atomic number decreases by 2✓ CorrectB.mass number decreases by 2, atomic number decreases by 4C.mass number is unchanged, atomic number decreases by 2D.mass number decreases by 4, atomic number increases by 2Answer: A. mass number decreases by 4, atomic number decreases by 2
Explanation: An α-particle carries away 2 protons and 2 neutrons, so A falls by 4 and Z falls by 2.
- Q3Easy
Radioactive decay of any nuclide follows kinetics of
A.zero orderB.second orderC.first order✓ CorrectD.third orderAnswer: C. first order
Explanation: The rate of disintegration is proportional to the number of undecayed nuclei present, −dN/dt = λN, which is a first order rate law.
- Q4Medium
A beam containing α, β and γ radiations is passed between two charged plates. The radiation that bends towards the negatively charged plate is
A.γ-radiationB.β-radiationC.α-radiation✓ CorrectD.none of them deflectsAnswer: C. α-radiation
Explanation: α-particles carry a +2 charge, so they are attracted to the negative plate; β-particles (negative) bend the other way and γ-rays, being uncharged, go straight.
- Q5Medium
²³⁸₉₂U emits one α-particle followed by two β⁻ particles. The nuclide finally formed is
A.²³⁴₉₀ThB.²³⁴₉₂U✓ CorrectC.²³⁰₉₀ThD.²³⁴₉₁PaAnswer: B. ²³⁴₉₂U
Explanation: α-loss gives A = 238 − 4 = 234 and Z = 92 − 2 = 90; the two β⁻ emissions then raise Z by 2 back to 92, giving ²³⁴₉₂U, an isotope of the parent.
- Q6Medium
The half-life of a radioactive isotope is 20 minutes. The fraction of the original sample left undecayed after 1 hour is
A.1/4B.1/8✓ CorrectC.1/16D.1/3Answer: B. 1/8
Explanation: 60 minutes is 3 half-lives, and the fraction left is (1/2)³ = 1/8.
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Start this chapter free →Nuclear Chemistry and Radioactivity — FAQs
What are the key concepts in Class 11 Chemistry Nuclear Chemistry and Radioactivity?+
Ordinary chemistry rearranges electrons; nuclear chemistry changes the nucleus itself. Beginning with Becquerel's accidental discovery in 1896 that uranium salts fog a wrapped photographic plate, this chapter looks at the three natural radiations α, β and γ and how they differ in charge, mass, ionising power and penetrating power. It then explains why some nuclei are unstable in terms of the neutron-to-proton ratio and the band of stability, works through the decay modes (α, β⁻, β⁺ and electron capture) and the group displacement law, treats decay as a first order rate process with a decay constant, half-life and average life, and finally covers artificial transmutation, fission, fusion, mass defect and binding energy, nuclear reactors and the everyday uses of radioisotopes in dating, medicine and agriculture. Key ideas include Radioactivity, Alpha, beta and gamma radiation, n/p ratio and the band of stability, Modes of decay.
What does Class 11 Chemistry Chapter 307 (Nuclear Chemistry and Radioactivity) cover on XamBaaz?+
It has 40 NCERT-based MCQs on "Nuclear Chemistry and Radioactivity": 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 "Nuclear Chemistry and Radioactivity" questions free to practise?+
Yes. Sign in with Google to practise "Nuclear Chemistry and Radioactivity" free. Full unlimited access is ₹999/year on a launch offer until 1 December 2026. No chapter is charged separately.
How should I revise "Nuclear Chemistry and Radioactivity" 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 "Nuclear Chemistry and Radioactivity" 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 "Nuclear Chemistry and Radioactivity" 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 Nuclear Chemistry and Radioactivity (Class 11 Chemistry)?+
The questions that matter most test Radioactivity, Alpha, beta and gamma radiation, n/p ratio and the band of stability, Modes of decay. 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 Nuclear Chemistry and Radioactivity?+
Yes — Class 11 Chemistry Nuclear Chemistry and Radioactivity 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.