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Physics

Nuclei

Composition and size of the nucleus, mass defect, binding energy per nucleon, and nuclear fission and fusion make up this chapter. NEET asks short numericals on mass-energy conversion and Q-values, alongside recall on the binding energy curve.

Exam rules change between cycles. Confirm dates, syllabus and pattern against NTA's official site. We are not NTA.

Weightage: what the paper actually did

Nuclei carried 2 questions in the NEET 2026 paper. One paper is a data point, not a destiny: NTA moves weight between chapters every cycle, which is why the weightage tables deserve care. The stable facts are the paper's shape: 180 questions, 720 marks, +4 right, −1 wrong.

Sample PYQs from this chapter

Real questions NTA asked from Nuclei, with the answer and the working. Try before you peek.

Question 1 · NEET 2026

An unknown nucleus has a nuclear density of 2.29×10172.29 \times 10^{17} kg/m3^3 and mass of 19.926×10−2719.926 \times 10^{-27} kg. Its mass number AA is approximately: (Take R0=1.2×10−15R_0 = 1.2 \times 10^{-15} m, 4π=12.564\pi = 12.56)
  1. A.12
  2. B.20
  3. C.16
  4. D.19
Answer and explanation

Answer: A

Using density = mass/volume with volume =43πR3= \frac{4}{3}\pi R^3 and R=R0A1/3R = R_0 A^{1/3}, we get 43πR03A=mρ\frac{4}{3}\pi R_0^3 A = \frac{m}{\rho}. Solving, A=mρ⋅34πR03=19.926×10−27×32.29×1017×12.56×(1.2×10−15)3≈12A = \frac{m}{\rho}\cdot\frac{3}{4\pi R_0^3} = \frac{19.926\times10^{-27}\times3}{2.29\times10^{17}\times12.56\times(1.2\times10^{-15})^3} \approx 12. Why the other options are wrong: - (B) Overestimate from arithmetic error. - (C) Common carbon-adjacent guess, incorrect here. - (D) Overestimate.

Question 2 · NEET 2026

Four statements are given (AA is mass number). Choose the correct answer from the options given below: I. The volume of a nucleus is proportional to A1/3A^{1/3}. II. The volume of a nucleus is proportional to AA. III. The difference in mass of an atom and its nucleus is called the mass defect. IV. The difference in mass of a nucleus and its constituents is called the mass defect.
  1. A.A and C are true, but B and D are false
  2. B.B and C are true, but A and D are false
  3. C.A and D are true, but B and C are false
  4. D.B and D are true, but A and C are false
Answer and explanation

Answer: D

Nuclear radius r=r0A1/3r = r_0 A^{1/3}, so volume ∝r3∝A\propto r^3 \propto A (statement B correct, A wrong). The mass defect is the difference between the total mass of the constituent nucleons and the actual mass of the nucleus (statement D correct, C wrong). Hence only B and D are true. Why the other options are wrong: - (A) Volume ∝A1/3\propto A^{1/3} is false; C mislabels mass defect. - (B) C is false (mass defect uses constituents, not atom). - (C) A is false; volume ∝\propto A not A1/3A^{1/3}.

How to practise Nuclei

Chapter by chapter, against real past-paper questions, on a screen: NEET is computer based from 2027. Read the chapter once, then attempt its PYQs until your accuracy stops climbing, and let the wrong answers tell you which lines to reread. If the chapter keeps refusing to stick, that has its own guide. There is also a free 12-question mock on the exam screen.

Nearby Physics chapters

Questions

How many questions did Nuclei have in NEET 2026?

Nuclei carried 2 questions in the NEET 2026 paper. Weightage shifts between cycles, so treat it as a probability, not a promise.

Where can I practise Nuclei PYQs for NEET?

In the BrainIt app, free until the 2027 exam: its bank holds 50,000 past NTA questions tagged to all 83 chapters, including this one, with accuracy tracked per chapter. Sample questions from this chapter are on this page.

Is Nuclei important for NEET 2027?

It is part of the Physics syllabus the paper draws from, and NEET 2027 is computer based, so practise it on a screen. Your own accuracy in the chapter matters more than any weightage table: a heavy chapter you already score well on needs less time than a light one you keep missing.

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