Nuclei: Class 12 Previous Year Questions

Nuclei questions asked in CBSE board exams

Repeated questions first. Open the free app to see each question as it appeared in the paper, with its marking scheme.

1. (a) Consider the following nuclides : 3 12 6C, 198 80Hg, 14 6C, 197 79Au Group them into isotopes and isotones. (b) How does the size of a nucleus depend on its mass number A ? Hence prove that the density of nucleus is a constant, independent of A, for all nu…
   Board 20263 marksshort answer
2. The ‘distance of closest approach’ of an alpha-particle is ‘d’ when it moves with a velocity  head-on towards the target nucleus. If the velocity of alpha particle is halved, the new ‘distance of closest approach’ will be – 1 (A) d 2 (B) 2d (C) d 4 (D) 4d
   Board 20261 markMCQ
3. ( ) p 15. Reason (A) : The mass of a nucleus is less than the sum of the masses of the constituent nucleons. 1 Reason (R) : Energy is absorbed when the nucleons are bound together to form a nucleus.
   Board 20261 markvery short
4. l. Which of the following figures correctly represent the shape of curve of binding energy per nucleon as a function of mass number ? B.E. B.E. (A) (B) 56 56 B.E. B.E. (C) (D) 80 80
   Board 20251 markMCQ
5. (a) Define ·Mass defect' and ·Binding energy' of a nucleus. Describe ·Fission process' on the basis of binding energy per nucleon. (b) A deuteron contains a proton and a neutron and has a mass of 2.013553 u. Calculate the mass defect for it in u and its energy…
   Board 20253 marksshort answer
6. (a) Show the variation of binding energy per nucleon with mass number. Write the significance of the binding energy curve. (b) Two nuclei with lower binding energy per nucleon form a nuclei with more binding energy per nucleon. (i).What type of nuclear reactio…
   Board 20253 marksshort answer
7. H$moB© b|g Xmo n¥îR>m| go {Kam H$moB© nmaXeu _mÜ`_ hmoVm h¡ {OgH$m EH$ AWdm XmoZm| n¥îR> Jmobr` hmoVo h¢ & {H$gr b|g H$s \$moH$g Xÿar CgHo$ XmoZm| n¥îR>m| H$s dH«$Vm {ÌÁ`mAm| Am¡a b|g Ho$ nXmW© Ho$, Cg nXmW© Ho$ gmnoj {Oggo b|g {Kam h¡, AndV©Zm§H$ Ûmam {ZYm©[a…
   Board 20244 markscase-based
8. An alpha particle approaches a gold nucleus in Geiger-Marsden experiment with kinetic energy K. It momentarily stops at a distance d from the nucleus and reverses its direction. Then d is proportional to : (A) K 1 (B) K (C) K 1 (D) K
   Board 20241 markMCQ
9. The curve of binding energy per nucleon as a function of atomic mass number has a sharp peak for helium nucleus. This implies that helium nucleus is (a) radioactive (b) unstable (c) easily fissionable (d) more stable nucleus than its neighbours
   Board 20231 markMCQ
10. (H$) hmBS´>moOZ na_mUw Ho$ {bE D$Om© ñVa AmaoI It{ME & nam~¢JZr joÌ, Ñí` joÌ Am¡a Adaº$ joÌ H$s lo{U`m| Ho$ VXZwê$n g§H«$_Um| H$mo A§{H$V H$s{OE & 3 AWdm (I) {d{^Þ Zm{^H$m| Ho$ {bE Ðì`_mZ g§»`m Ho$ Ho$ {dMaU H$mo Xem©Zo Ho$ {bE AmaoI It{ME Am¡a BgH$s Xmo {deof…
    Board 20233 marksshort answer
11. (a) (i) Distinguish between nuclear fission and fusion giving an example of each. (ii) Explain the release of energy in nuclear fission and fusion on the basis of binding energy per nucleon curve. OR (b) (i) How is the size of a nucleus found experimentally ? …
    Board 20233 marksshort answer
12. (a) What is meant by ionisation energy ? Write its value for hydrogen atom. OR (b) Define the term, mass defect. How is it related to stability of the nucleus ?
    Board 20232 marksshort answer
13. Calculate the energy released in MeV in the following reaction : ·,He + n Given : H)= 2.014102 u H)= 3.016049 u He)= 4.002603 u mn = 1.008665 u Explain with the help of a suitable diagram, the phenomenon on which an optical fibre works. Mention any two uses of…
    Board 20221 markvery short
14. (a) Depict the variation of the potential energy of a pair of nucleons with the separation between them. (b) Imagine the fission of a Fe 56 26 into two equal fragments of Al 28 13 nucleus. Is the fission energetically possible ? Justify your answer by working …
    Board 20221 markvery short
15. Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (A), (B), (C), and (B) as given below. Assertion (A) : The curve between the binding energy per nucleon versus ma…
    CBSE practice 2022-231 markAssertion-Reason
16. The atomic mass of 168O is 15.99493 u. Calculate the binding energy per nucleon of the oxygen nucleus. (Given: mass of proton = 1.00727 u, mass of neutron = 1.00866 u, 1 u = 931.5 MeV/c2)
    Sample paper 2026-273 marksshort answer
17. (a) Given are two nuclei: 𝐻 1 3 and 𝐻𝑒 2 3 . Justify that these two nuclei have the same radii. (b) A scientist hypothesizes the existence of a neutral particle of mass 2.0272 u which consists of two neutrons only. Take mass of neutron = 1.0086 u. i. What is t…
    CBSE practice 2021-223 marksshort answer
18. Identify if the two nuclear reactions mentioned below are endothermic or exothermic. Show your calculations. Use the information below to answer the question:
    CBSE practice 2023-243 marksshort answer
19. By what factor does kinetic and potential energy of an electron in a hydrogen atom change as it moves from n = 1 to n =3? OR (a) Multiplication factor or reproduction factor K for a nuclear reactor is defined as number of fission reactions produced by a given …
    CBSE practice 2022-232 marksshort answer
20. Find the electrical potential energy of the two identical nuclei formed just after the fission of a 100X250 nucleus.(R0=1.28 X 10-15)
    CBSE practice 2023-242 marksshort answer

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