CHAPTER - 13

NUCLEI

1. Nucleons are
A) Protons and neutrons B) Neutrons and electrons
C) Protons and electrons D) All of these
2. What is the approximate ratio of volume of a nucleus to the volume of an atom ?
A) 10-34 B) 10-20
C) 10-12 D) 10-10
3. The set which represents the isotope, isobar and isotones respectively is
A) (21𝐻 , 31𝐻 ), ( 197 198 3
79𝐴𝑢 , 80𝐻𝑔) and ( 2𝐻𝑒 , 1𝐻 )
2

B) ( 32𝐻𝑒, 11𝐻 ), (197 198 1 3

79𝐴𝑢 , 80𝐻𝑔) and ( 1𝐻 , 1𝐻 )
C) ( 32𝐻𝑒, 31𝐻 ),(21𝐻 , 31𝐻 ) and ( 197 198
79𝐴𝑢 , 80𝐻𝑔)
D) (21𝐻 , 31𝐻 ), ( 32𝐻𝑒 , 31𝐻 ) and ( 197 198
79𝐴𝑢 , 80𝐻𝑔 )
4. 31𝐻 𝑎𝑛𝑑 32𝐻𝑒 atoms are example for
A) Isobars B) Isotones
C) Isotopes D) Isomers.
37 39
5. 17𝐶𝑙 𝑎𝑛𝑑 19𝐾 atoms are example for
A) Isobars B) Isotones
C) Isotopes D) Isomers.
1 2 3
6. 1𝐻 , 1𝐻 𝑎𝑛𝑑 1𝐻 atoms are example for
A) Isobars B) Isotones
C) Isotopes D) Isomers
7. Order of magnitude of density of uranium nucleus is
A) 1020kgm-3 B) 1017kgm-3
C) 1014kgm-3 D) 1011kgm-3
8. The force between two protons is same as the force between proton and neutron. The nature of the force
is
A) Electrical force B) Weak Nuclear force
C) Gravitational force D) Strong nuclear force
9. The nuclear force
A) Is purely an electrostatic force B) Obeys inverse square law of distance
C) Is equal in strength to gravitational field D) Is a short range force.
10. All the nucleons in an atom are held by
A) Nuclear forces B) Vander Waal’s force
C) Tensor forces D) Coulomb forces
11. Carbon dating is best suited for determining the age of fossils ., if their age in years is of the order of
A) 103 B) 104
5
C) 10 D) 106
12. Which of the following can be emitted by radioactive substances during their decay?
A) Neutrinos B) Helium nuclei
C) Electrons D) All of these.
13. Pick out the incorrect statement from the following:
A) 𝛽 − emission from the nucleus is always accompanied with a neutrino.
B) The energy of the α-particle emitted from a given nucleus is always constant.
 C) ϒ- ray emission makes the nucleus more stable.
D) Nuclear force is charge independent.
14. Consider α and β particles and ϒ- rays each having an energy of 0.5MeV. In the increasing order of
penetrating power, the radiation are respectively:
A) α, β, ϒ B) α, ϒ, β
C) β, ϒ, α D) ϒ, β, α
15. An electron emitted in beta radiation originates from
A) Inner orbits of atom
B) free electrons existing in the nucleus.
C) decay of neutrons in a nuclei.
D) photon escaping from the nucleus.
16. Complete the series; 2He6 → 3Li6 + -1e0 + _____
A) Neutrino B) Antineutrino
C) Proton D) Neutron
1 + 4
17. The equation 4 1𝐻 → 2𝐻𝑒 2+ + 2𝑒 − + 26 MeV represents
A) β–decay B) ϒ-decay
C) fusion D) fission
18. Light energy emitted by star is due to
A) Breaking of nuclei. B) Joining of nuclei
C) Burning of nuclei. D) Reflection of solar light.
19. In nuclear reactors, the control rods are made of
A) Cadmium B) graphite
C) Krypton D) Plutonium.
20. Fast neutrons can easily be slowed down by
A) The use of lead shielding.
B) Passing them through water.
C) Elastic collision with heavy nuclei.
D) Applying a strong electric field.
21. Fission of nuclei is possible because the binding energy per nucleon in them
A) Increases with mass number at low mass numbers.
B) Decreases with mass number at low mass numbers.
C) Increases with mass number at high mass number.
D) Decreases with mass number at high mass number.
𝑅
22. The graph of log⌈𝑅 ⌉ versus log A where R= radius of a nucleus and A = its mass number is
𝑜
A) A straight line B) a parabola
C) an ellipse D) none of the above.
23. Which particle is emitted beta decay?
A) Protons B) Neutron
C) nuclei D) A high energy electron.
24. Which is not a characteristics of gamma radiation ?
A) Stopped by several feet of concrete or several inches of lead.
B) High energy, high penetration.
C) Stopped by thin metal.
D) Most dangerous type of radiation.
25. What is radioactive decay ?
 A) The spontaneous breakdown of an atomic nucleus resulting in a release of energy and matter.
B) The spontaneous breakdown of an atomic nucleus resulting in only matter release.
C) The spontaneous breakdown of an atomic nucleus resulting in only energy release.
D) The decay of the use of radios and the increased use of televisions.
26. Which is not true of radioactive decay?
A) Radioactivity can be useful.
B) It happens only in nuclear power plants
C) It is hazardous to human health
D) It is a result of instability in atoms.
27. Isotopes of the same element have different _______
A) Number of electrons B) Number of neutrons
C) Number of protons D) Symbols
28. When does radioactive decay occur?
A) When the electrons of an isotope are shared with another isotope.
B) When the electrons of an isotope are spinning.
C) When the nucleus of an isotope is unstable.
D) When the nucleus of an isotope is stable.
29. Two smaller nuclei combines to form a larger nucleus is
A) Fission B) Fusion
C) gamma radiation D) half life
30. The splitting of a nucleus into smaller nuclei is
A) Fission B) Fusion
C) gamma radiation D) half life
31. Which atoms combine together during fusion reaction on the Sun ?
A) Helium and Hydrogen atoms B) Hydrogen and Carbon atoms
C) Hydrogen atoms D) Hydrogen and Lithium atoms
32. Very high temperature and pressure is required to:
A) Fission B) Fusion
C) gamma radiation D) half life
33. One disadvantage of nuclear energy is ___
A) It emits large amounts of pollution into the atmosphere.
B) It is a fossil fuel.
C) There are no disadvantages.
D) It leaves behind radioactive waste.
34. One advantage of nuclear energy over coal energy is _____
A) The nuclear plant emits more greenhouse gases.
B) There is very little dangerous waste with nuclear energy.
C) The nuclear plant does not emit as many greenhouse gases.
D) It is very cheap to build and maintain a nuclear power plant.
35. A radioactive nucleus emits a beta particle, then the parent and daughter nuclei are
A) Isotones B) Isotopes
C) Isomers D) Isobars
36. Which of the following are not emitted by radioactive substances?
A) Protons B) Electrons
C) Gamma Rays D) Helium Nuclei
37. A nucleus undergoes gamma decay due to
A) Excess of neutrons B) Excess of protons
C) Its excited state D) Large mass
38. Isotones have the same number of
A) Protons B) Electrons
C) Neutrons D) All of the above
39. If ‘K’ is a measure of the growth rate of neutrons in a reactor, then the value of ‘K’ is for the chain
reaction gradually dies out is
A) K =1 B) K<1
C) K>1 D) K=0
40. In proton-proton cycle, the approximate amount of energy released is
A) 26.7 MeV B) 20.1 MeV
C) 28.9 MeV D) 22.5 MeV

ANSWERS;

QN AN QN AN QN AN QN AN
1 A 11 B 21 D 31 C
2 C 12 D 22 A 32 B
3 D 13 A 23 D 33 D
4 A 14 A 24 C 34 C
5 B 15 C 25 A 35 D
6 C 16 B 26 B 36 A
7 B 17 C 27 B 37 C
8 D 18 B 28 C 38 C
9 D 19 A 29 B 39 B
10 A 20 B 30 A 40 A

FILL IN THE BLANKS:

1. Protons and neutrons present in the nucleus are together called the nucleons.
2. The number of proton present in the nucleus is called the atomic number.
3. The number of nucleons in the nucleus is called the atomic mass number.
4. Nuclei of the same element having same atomic number but different mass number are called isotopes.
5. Nuclei of different elements having same mass number but different atomic number are called isobars.
6. Nuclei of different elements having same number of neutrons are called isotones.
7. Neutrons were discovered by James Chadwick.
8. Mass spectrograph is the instrument use to measure the atomic masses.
9. The order of nuclear density is 1017kgm-3.
10. Energy equivalent of 1 a m u is 931.5MeV.
11. During the pair annihilation , the energy is released in the form of ϒ-rays(Photons).
12. The difference between the sum of the masses of the nucleons forming the nucleus and the rest mass of
the nucleus is called mass defect.
13. The minimum amount of energy required to split the nucleus into its constituents is called nuclear
binding energy.
14. Binding energy per nucleon is maximum for Fe56.
15. Binding energy per nucleon is minimum for U238.
16. The forces that hold the nucleons together inside the nucleus are called nuclear forces.
17. Nuclear forces are strongest forces in nature.
18. Nuclear forces are short range forces.
19. The amount of energy released in per fission of 92U235 is about 200MeV.
20. A nuclear reactor is a device which produces nuclear energy at a steady state.
21. The fission chain reaction will be critical and the chain reaction is just sustained when multiplication
factor of a fissionable mass ,K=1.
22. The fission chain reaction gradually dies out, when K<1.
23. The fission chain reaction grows exponentially, when K>1.
24. A material used to slowdown the neutrons to thermal energies in a nuclear reactor is called moderator.
25. Control rods are used for absorption of excess neutrons in a nuclear reactor.
26. The phenomenon by which energy is produced in a star is Nuclear Fusion.
27. Nuclear fusion reactions require very high temperature of the order of 109K.
28. Nuclear fission is the principle of atom bombs.
29. Nuclear fusion is the principle of hydrogen atoms.
30. The phenomenon of spontaneous disintegration of heavy nuclei with emission of certain radiations is
called radioactivity.
31. Henry Becquerel discovered radioactivity.
32. Αlpha-particle is a helium nucleus consists of two protons and two neutrons.
33. Gamma rays are the uncharged radiation emitted by radioactive substances.
34. The SI unit of activity is becquerel (Bq).
35. The practical unit of activity is curie (Ci).
36. If mean life of a radioactive element is one year, then its half year is 0.693 year.
37. In α-decay, atomic number decreases by two units.
38. In α-decay, mass number decreases by four units.
39. In negative β-decay , the atomic number increases by one unit.
40. Antineutrino is emitted in negative β-decay.
41. In positive β-decay, the atomic number decreases by one unit.
42. Neutrino is emitted in positive β-decay.
43. In proton-proton cycle, the approximate amount of energy released is 26.7MeV.
44. The principle used in nuclear reactor is controlled fissioin chain reaction.