Read the following passage and answer the questions.
Nuclear power stations and the sun both draw their energy from atomic nuclei. In a reactor, a neutron strikes a nucleus of uranium-235. The nucleus splits into two nuclei and a few neutrons. About 200 MeV of energy is released each time a uranium nucleus splits in this way. A reactor uses this energy to produce electricity. The sun works in a different way. In its core, very light nuclei, such as those of hydrogen, join to form heavier nuclei. These nuclei are positively charged and repel each other. So the joining takes place only at a very high temperature, where the nuclei move fast enough to come very close. Scientists are also trying to make light nuclei join in a controlled way on the earth.
Match List-I with List-II.
| List-I (reaction) | List-II (number of neutrons produced) |
|---|---|
| (A) \({}^{1}_{0}\mathrm{n}+{}^{235}_{92}\mathrm{U}\rightarrow{}^{144}_{56}\mathrm{Ba}+{}^{89}_{36}\mathrm{Kr}+\text{neutrons}\) | (I) 1 |
| (B) \({}^{1}_{0}\mathrm{n}+{}^{235}_{92}\mathrm{U}\rightarrow{}^{132}_{50}\mathrm{Sn}+{}^{100}_{42}\mathrm{Mo}+\text{neutrons}\) | (II) 2 |
| (C) \({}^{1}_{0}\mathrm{n}+{}^{235}_{92}\mathrm{U}\rightarrow{}^{137}_{52}\mathrm{Te}+{}^{97}_{40}\mathrm{Zr}+\text{neutrons}\) | (III) 3 |
| (D) \({}^{2}_{1}\mathrm{H}+{}^{2}_{1}\mathrm{H}\rightarrow{}^{3}_{2}\mathrm{He}+\text{neutrons}\) | (IV) 4 |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A)-(III), (B)-(IV), (C)-(II), (D)-(I)
The mass number is the same on both sides of a nuclear reaction. Each neutron has mass number 1, so the number of neutrons is the mass number left over after the product nuclei.
(A) \( {}^{1}_{0}\mathrm{n}+{}^{235}_{92}\mathrm{U}\rightarrow{}^{144}_{56}\mathrm{Ba}+{}^{89}_{36}\mathrm{Kr} \) — This matches (III) 3. The left side has \( 1+235=236 \). The products have \( 144+89=233 \), so \( 236-233=3 \).
(B) \( {}^{1}_{0}\mathrm{n}+{}^{235}_{92}\mathrm{U}\rightarrow{}^{132}_{50}\mathrm{Sn}+{}^{100}_{42}\mathrm{Mo} \) — This matches (IV) 4. The products have \( 132+100=232 \), and \( 236-232=4 \).
(C) \( {}^{1}_{0}\mathrm{n}+{}^{235}_{92}\mathrm{U}\rightarrow{}^{137}_{52}\mathrm{Te}+{}^{97}_{40}\mathrm{Zr} \) — This matches (II) 2. The products have \( 137+97=234 \), and \( 236-234=2 \).
(D) \( {}^{2}_{1}\mathrm{H}+{}^{2}_{1}\mathrm{H}\rightarrow{}^{3}_{2}\mathrm{He} \) — This matches (I) 1. The left side has \( 2+2=4 \), and helium-3 takes 3, so \( 4-3=1 \).
The atomic numbers balance in every case, for example \( 50+42=92 \) in (B) and \( 52+40=92 \) in (C).
NCERT (2026-27):
Fission – “… a uranium isotope 23592U bombarded with a neutron breaks into two intermediate mass nuclear fragments”
\( {}^{1}_{0}\mathrm{n}+{}^{235}_{92}\mathrm{U}\rightarrow{}^{236}_{92}\mathrm{U}\rightarrow{}^{144}_{56}\mathrm{Ba}+{}^{89}_{36}\mathrm{Kr} \)\( +\,3\,{}^{1}_{0}\mathrm{n} \)\( \qquad (13.10) \)
Example 13.4 (Solution) – “… However, the number of protons and the number of neutrons are both separately conserved in a nuclear reaction. …”
Nuclear fusion – energy generation in stars
\( {}^{2}_{1}\mathrm{H}+{}^{2}_{1}\mathrm{H}\rightarrow{}^{3}_{2}\mathrm{He} \)\( +\ \mathrm{n} \)\( +\ 3.27\ \mathrm{MeV}\qquad [13.13(b)] \)