Assertion and Reason Questions Chapter-13 Nuclei
Assertion (A) and other labelled Reason (R). Select the correct answer to these
questions from the options as given below.
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true, but R is false.
D. A is false, but R is true.
1. Assertion (A): The nucleus of an atom is positively charged.
Reason (R): The nucleus contains protons, which have a positive
charge.
2. Assertion (A): Neutrons play a crucial role in the stability of a nucleus.
Reason (R): Neutrons contribute to the strong nuclear force
without repulsion.
3. Assertion (A): Nuclear fission can release a large amount of energy.
Reason (R): The binding energy of the resulting nuclei is greater
than that of the original nucleus.
4. Assertion (A): The mass of a nucleus is less than the sum of the masses of
its constituent protons and neutrons.
Reason (R): This mass difference is due to the binding energy of
the nucleus.
5. Assertion (A): Radioactive decay is a random process.
Reason (R): The half-life of a radioactive substance is a
constant.
6. Assertion (A): Alpha particles have a greater mass than beta particles.
Reason (R): Alpha particles consist of two protons and two
neutrons.
7. Assertion (A): The strong nuclear force is responsible for holding the
nucleus together.
Reason (R): The strong force acts only at very short distances,
typically on the order of femtometers.
8. Assertion (A): In beta decay, a neutron is converted into a proton.
Reason (R): This process emits a beta particle and an
antineutrino.
9. Assertion (A): The energy released in nuclear reactions is often measured in
MeV.
Reason (R): The MeV scale is more suitable for nuclear processes
than joules.
10. Assertion (A): The half-life of a radioactive isotope is not affected by
external conditions.
Reason (R): Half-life is an intrinsic property of the isotope.
11. Assertion (A): Nuclear fusion occurs at extremely high temperatures.
Reason (R): High temperatures provide sufficient energy to
overcome the electrostatic repulsion between nuclei.
12. Assertion (A): The concept of binding energy per nucleon helps in
understanding nuclear stability.
Reason (R): Higher binding energy per nucleon indicates a more
stable nucleus.
13. Assertion (A): Fission and fusion reactions can both release energy.
Reason (R): Both processes involve changes in binding energy.
14. Assertion (A): The emission of gamma rays does not change the atomic number
of the nucleus.
Reason (R): Gamma emission involves a transition to a lower energy
state.
15. Assertion (A): Heavy nuclei are more likely to undergo fission.
Reason (R): The strong nuclear force is insufficient to counteract
electromagnetic repulsion in heavy nuclei.
16. Assertion (A): A stable nucleus has a specific ratio of neutrons to protons.
Reason (R): This ratio varies for different elements and
determines nuclear stability.
17. Assertion (A): The stability of a nucleus can be assessed using the liquid
drop model.
Reason (R): The liquid drop model treats the nucleus like a
droplet of incompressible fluid.
18. Assertion (A): The strong nuclear force operates between all nucleons.
Reason (R): The strong force is much stronger than the
electromagnetic force at short ranges.
19. Assertion (A): Nuclear reactions can be initiated by bombarding nuclei with
neutrons.
Reason (R): Neutrons are uncharged and can penetrate the nucleus
without being repelled.
20. Assertion (A): Nuclear reactions are not limited by the energy levels of the
reactants.
Reason (R): The energy released in nuclear reactions is
significantly higher than in chemical reactions.
21. Assertion (A): The mass-energy equivalence principle explains the energy
release in nuclear reactions.
Reason (R): Mass can be converted into energy according to
E=m \(\ c^{2}\).
22. Assertion (A): The critical mass of a fissile material is necessary for a
chain reaction.
Reason (R): A chain reaction occurs only when enough material is
present to sustain it.
23. Assertion (A): Isotopes of an element have different nuclear stability.
Reason (R): Stability is influenced by the ratio of neutrons to
protons in the nucleus.
24. Assertion (A): Alpha decay results in the loss of two protons and two
neutrons from the nucleus.
Reason (R): Alpha particles are identical to helium nuclei.
25. Assertion (A): Nuclear decay can be detected using a Geiger counter.
Reason (R): Geiger counters are sensitive to ionizing radiation
emitted during decay.
26. Assertion (A): The binding energy of a nucleus increases with the number of
nucleons.
Reason (R): More nucleons contribute to stronger interactions.
27. Assertion (A): The mass defect is crucial in calculating nuclear binding
energy.
Reason (R): The binding energy is the energy required to
disassemble a nucleus into its constituent nucleons.
28. Assertion (A): Nuclear reactors utilize fission reactions to generate
electricity.
Reason (R): Fission releases heat, which is used to produce steam
for turbines.
29. Assertion (A): The neutron-to-proton ratio is critical for determining
nuclear stability.
Reason (R): Nuclei with too many or too few neutrons compared to
protons tend to be unstable.
30. Assertion (A): The nuclear shell model describes nucleon arrangement in the
nucleus.
Reason (R): Nucleons occupy discrete energy levels similar to
electrons in an atom.
31. Assertion (A): The process of nucleosynthesis occurs in stars.
Reason (R): Fusion reactions in stars create heavier elements from
lighter ones.
32. Assertion (A): The liquid drop model and the shell model are both essential
for understanding nuclear physics.
Reason (R): Each model addresses different aspects of nuclear
behavior.
33. Assertion (A): Nuclear energy can be harnessed for peaceful purposes.
Reason (R): Nuclear technology is used for electricity generation,
medicine, and research.
34. Assertion (A): Nuclear magnetic resonance (NMR) uses properties of atomic
nuclei.
Reason (R): NMR is a technique based on the absorption of
electromagnetic radiation by nuclei in a magnetic field.
35. Assertion (A): The principle of conservation of nucleon number applies in
nuclear reactions.
Reason (R): The total number of nucleons before and after a
reaction remains constant.
36. Assertion (A): The stability of a nucleus can change under extreme
conditions.
Reason (R): High energy inputs can lead to nuclear reactions and
instability.
37. Assertion (A): Nuclear reactions can produce both heavy and light nuclei.
Reason (R): The type of reaction determines the resulting
products.
38. Assertion (A): The average binding energy per nucleon generally increases
with atomic mass up to iron.
Reason (R): Heavier nuclei have greater nuclear forces acting on
them.
39. Assertion (A): Nuclei with even numbers of protons and neutrons are usually
more stable.
Reason (R): Pairing effects lead to greater nuclear stability.
40. Assertion (A): The decay of radioactive materials is a first-order process.
Reason (R): The rate of decay is proportional to the remaining
quantity of the substance.
41. Assertion (A): In beta decay, a neutron is converted into a proton.
Reason (R): An electron is emitted along with an antineutrino
during this process.
42. Assertion (A): The half-life of a radioactive isotope is constant and unique
to each isotope.
Reason (R): Half-life does not change with the amount of substance
present.
43. Assertion (A): Nuclear fusion has the potential to provide almost limitless
energy.
Reason (R): Fusion reactions produce more energy than fission
reactions.
44. Assertion (A): High-energy gamma rays can penetrate matter deeply.
Reason (R): Gamma rays have no mass and no charge, allowing them
to bypass material barriers.
45. Assertion (A): Neutrons play a crucial role in sustaining nuclear fission
reactions.
Reason (R): Neutrons initiate further fission reactions by
colliding with other nuclei.
46. Assertion (A): Nuclear decay chains can lead to the formation of stable
isotopes.
Reason (R): A series of decays transforms unstable isotopes into
stable ones over time.
47. Assertion (A): Radioactive decay follows a predictable pattern over time.
Reason (R): The decay constant for a radioactive substance is
unique and constant.
48. Assertion (A): Nuclear reactions can release large amounts of energy
compared to chemical reactions.
Reason (R): The energy changes in nuclear reactions are due to
changes in binding energy.
49. Assertion (A): Uranium-235 is commonly used as fuel in nuclear reactors.
Reason (R): Uranium-235 is a fissile isotope capable of sustaining
a chain reaction.
50. Assertion (A): The process of alpha decay decreases the mass of the nucleus.
Reason (R): An alpha particle consists of two protons and two
neutrons.