General Properties of Nuclei, 60 mcqs on it with explained answers
Here are 60 multiple choice questions (MCQs) on the general properties of nuclei, each with an explained answer. These cover core concepts such as nuclear composition, mass, size, binding energy, and nuclear forces.
### MCQs on General Properties of Nuclei
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1. **What is the central core of every atom?**
- a) Electron
- b) Proton
- c) Nucleus
- d) Neutron
- **Answer:** c) Nucleus
**Explanation:** The nucleus is the central core, containing more than 99% of the atom’s mass and all its positive charge [2].
2. **Which property of the nucleus determines the atomic number?**
- a) Number of neutrons
- b) Number of protons
- c) Number of electrons
- d) Mass number
- **Answer:** b) Number of protons
**Explanation:** The atomic number is equal to the number of protons in the nucleus [2][9].
3. **What is the typical size of a nucleus?**
- a) $$10^{-10} $$ m
- b) $$10^{-15} $$ m
- c) $$10^{-8} $$ m
- d) $$10^{-12} $$ m
- **Answer:** b) $$10^{-15} $$ m
**Explanation:** The nucleus has a size of about $$10^{-15} $$ m, much smaller than the atom itself [2].
4. **Nucleons refer to which particles?**
- a) Protons only
- b) Neutrons only
- c) Protons and neutrons
- d) Electrons and protons
- **Answer:** c) Protons and neutrons
**Explanation:** Nucleons are the particles (protons and neutrons) found in the nucleus [3].
5. **For a nuclear fusion process, the suitable nuclei are:**
- a) Any nuclei
- b) Heavy nuclei
- c) Lighter nuclei
- d) Nuclei in middle of periodic table
- **Answer:** c) Lighter nuclei
**Explanation:** Fusion combines lighter nuclei into heavier ones; lighter nuclei undergo fusion more easily [2].
6. **Which particle can be added to the nucleus without changing chemical properties?**
- a) Neutron
- b) Electron
- c) Proton
- d) Alpha particle
- **Answer:** a) Neutron
**Explanation:** Adding a neutron increases mass but does not alter chemical properties [2].
7. **Which force holds protons and neutrons together in the nucleus?**
- a) Gravitational
- b) Electromagnetic
- c) Nuclear force
- d) Weak force
- **Answer:** c) Nuclear force
**Explanation:** The strong nuclear force binds nucleons despite repulsion between protons [4].
8. **The mass of a nucleus is approximately:**
- a) The total mass of protons only
- b) The total mass of electrons
- c) The total mass of protons plus neutrons
- d) The total mass of protons plus electrons
- **Answer:** c) The total mass of protons plus neutrons
**Explanation:** Nucleus mass = sum of masses of protons and neutrons [1][5].
9. **Nucleus charge is equal to:**
- a) +Ze
- b) -Ze
- c) 0
- d) A+Z
- **Answer:** a) +Ze
**Explanation:** Nucleus charge = number of protons $$\times$$ charge of proton (+e) [1][5].
10. **Binding energy in nuclei per nucleon:**
- a) Increases continuously with mass number
- b) Decreases continuously with mass number
- c) Remains constant with mass number
- d) First increases then decreases
- **Answer:** d) First increases then decreases
**Explanation:** BE per nucleon rises with $$A$$, peaks at iron, then drops for heavier nuclei [2][3].
11. **The spin of a nucleus depends on:**
- a) Proton number only
- b) Neutron number only
- c) Unpaired nucleons
- d) Total number of nucleons
- **Answer:** c) Unpaired nucleons
**Explanation:** Nuclear spin arises from unpaired protons or neutrons [3].
12. **Which nuclear model assumes the nucleus is like a drop of liquid?**
- a) Liquid drop model
- b) Shell model
- c) Collective model
- d) Bohr model
- **Answer:** a) Liquid drop model
**Explanation:** The liquid drop model explains nuclear binding energy and fission [1].
13. **Which property of the nucleus largely determines its stability?**
- a) Mass number
- b) Binding energy
- c) Charge
- d) Volume
- **Answer:** b) Binding energy
**Explanation:** Stability is dependent on how much energy binds nucleons [7].
14. **Isotopes have:**
- a) Same A, different Z
- b) Same Z, different A
- c) Same A and Z
- d) Different A and Z
- **Answer:** b) Same Z, different A
**Explanation:** Isotopes share the same proton number, but differ in neutron numbers [7].
15. **What is the typical nuclear density?**
- a) Much less than atomic density
- b) About $$10^{17} $$ kg/m$$^3$$
- c) Zero
- d) About $$10^{3} $$ kg/m$$^3$$
- **Answer:** b) About $$10^{17} $$ kg/m$$^3$$
**Explanation:** Nuclear density is extremely high due to compact nucleons [1][3].
16. **For nuclei, mass density is:**
- a) Depends on mass number
- b) Depends on atomic number
- c) Constant
- d) Varies with element
- **Answer:** c) Constant
**Explanation:** Density is nearly constant for all nuclei because volume scales with nucleon count [4].
17. **Which of the following is NOT conserved in a nuclear reaction?**
- a) Mass
- b) Charge
- c) Momentum
- d) None
- **Answer:** a) Mass
**Explanation:** Mass can change due to conversion to energy (mass defect). Charge and momentum are always conserved [8].
18. **The process of radioactive decay changes:**
- a) Number of nucleons
- b) Mass number
- c) Proton or neutron number
- d) All of the above
- **Answer:** d) All of the above
**Explanation:** Decay can change mass number, nucleon type, or both [1].
19. **Nucleus with odd A (mass number) usually:**
- a) Is stable
- b) Has integer spin
- c) Has half-integer spin
- d) Is always radioactive
- **Answer:** c) Has half-integer spin
**Explanation:** Odd-A nuclei have half-integer (e.g., 1/2, 3/2) spins due to unpaired nucleon [3].
20. **The most stable nucleus is:**
- a) Hydrogen ($$^1H$$)
- b) Uranium ($$^{238}U$$)
- c) Iron ($$^{56}Fe$$)
- d) Gold ($$^{197}Au$$)
- **Answer:** c) Iron ($$^{56}Fe$$)
**Explanation:** Iron has the highest binding energy per nucleon, making it highly stable [7].
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1. **A free neutron decays into a proton but a free proton does not decay into a neutron because:**
- a) Proton is lighter
- b) Neutron is lighter
- c) Both are stable
- d) They repel each other
- **Answer:** a) Proton is lighter
**Explanation:** The neutron’s mass is higher than the proton’s, so neutron decay is energetically possible, but not vice versa[1].
2. **If the half-life of a radioactive element is 30 min, the fraction remaining after 90 min is:**
- a) 1/2
- b) 1/3
- c) 1/4
- d) 1/8
- **Answer:** d) 1/8
**Explanation:** After each half-life, half remains: 90 min = 3 half-lives, so (1/2)^3 = 1/8[1].
3. **The nucleus is:**
- a) Positively charged
- b) Negatively charged
- c) Neutral
- d) Variable in charge
- **Answer:** a) Positively charged
**Explanation:** The nucleus contains positively charged protons, so overall it is positive[1].
4. **A “Q value” in nuclear reactions refers to:**
- a) Quasiparticle value
- b) Energy released
- c) Charge
- d) Quality factor
- **Answer:** b) Energy released
**Explanation:** Q value is the net energy released in a nuclear reaction due to mass defect[2].
5. **Nuclear force operates predominantly over:**
- a) Infinite range
- b) 1 meter
- c) $$10^{-15}$$ meters (1 fm)
- d) 1 nanometer
- **Answer:** c) $$10^{-15}$$ meters
**Explanation:** The strong nuclear force is short-range, about 1 femtometer[2].
6. **In nuclear fission, typical main product is:**
- a) Helium
- b) Krypton
- c) Barium
- d) Oxygen
- **Answer:** c) Barium
**Explanation:** Fission, such as of uranium-235, commonly yields barium and krypton[2].
7. **Which best defines nuclear forces?**
- a) Attraction between protons and electrons
- b) Attraction between protons and neutrons
- c) Repulsion between protons and neutrons
- d) Attraction between electrons and neutrons
- **Answer:** b) Attraction between protons and neutrons
**Explanation:** This is the force binding nucleons in the nucleus[2].
8. **Nuclear force is:**
- a) Charge dependent
- b) Extremely long ranged
- c) Independent of charge
- d) Weaker than gravity
- **Answer:** c) Independent of charge
**Explanation:** Nuclear force is same between neutron-neutron, proton-proton, and proton-neutron pairs[2].
9. **If a nucleus loses a beta particle:**
- a) Proton number decreases by 1
- b) Neutron number decreases by 1, proton increases by 1
- c) Both decrease by 1
- d) Both increase by 1
- **Answer:** b) Neutron number decreases by 1, proton increases by 1
**Explanation:** Beta decay converts a neutron to proton[6].
10. **An isotope with no neutrons is:**
- a) Tritium
- b) Deuterium
- c) Protium
- d) Helium
- **Answer:** c) Protium
**Explanation:** Protium, the most common hydrogen isotope, has one proton and no neutrons[3].
11. **Magic numbers in nuclear physics refer to:**
- a) Electron configuration
- b) Stable nucleon numbers
- c) Neutron decay constants
- d) Isotope decay rates
- **Answer:** b) Stable nucleon numbers
**Explanation:** Certain neutron or proton counts confer extra stability to nuclei[7].
12. **The energy required to remove a nucleon from the nucleus is called:**
- a) Ionization energy
- b) Binding energy
- c) Fission energy
- d) Coulomb energy
- **Answer:** b) Binding energy
**Explanation:** Binding energy is what holds nucleons together in the nucleus[6].
13. **Fractional mass defect of nuclei is typically:**
- a) 1%
- b) 0.1%
- c) 0.01%
- d) 0.001%
- **Answer:** b) 0.1%
**Explanation:** Mass defect is a very small but non-zero proportion of total nucleon mass, often around 0.1%[6].
14. **Which of these is not a component of a nuclear reactor?**
- a) Turbine
- b) Heat exchanger
- c) CO2 emission mechanism
- d) Reaction chamber
- **Answer:** c) CO2 emission mechanism
**Explanation:** Nuclear reactors do not burn fuel in a way that releases CO2[3].
15. **A “strong” nuclear force is generally:**
- a) Attractive
- b) Always repulsive
- c) Weakest force
- d) Infinite range
- **Answer:** a) Attractive
**Explanation:** Nuclear force attracts nucleons inside the nucleus but becomes repulsive at very close range[3].
16. **The electric force between two protons at 1 fm is:**
- a) Much stronger than nuclear force
- b) Much weaker than nuclear force
- c) Same as nuclear force
- d) Always repulsive
- **Answer:** b) Much weaker than nuclear force
**Explanation:** The nuclear force predominates at short range, keeping protons bound[2].
17. **Which emission increases the atomic number of an atom?**
- a) Alpha
- b) Beta (minus)
- c) Beta (plus)
- d) Gamma
- **Answer:** b) Beta (minus)
**Explanation:** A neutron turns into a proton, increasing atomic number by 1[6].
18. **Radioactivity was first discovered by:**
- a) Marie Curie
- b) Henri Becquerel
- c) Ernest Rutherford
- d) J.J. Thomson
- **Answer:** b) Henri Becquerel
**Explanation:** Becquerel discovered radioactivity in uranium salts[6].
19. **Which law governs radioactive decay?**
- a) Law of constant proportions
- b) Law of mass action
- c) Exponential decay law
- d) Newton’s law
- **Answer:** c) Exponential decay law
**Explanation:** The decay follows a first-order exponential process[4].
20. **The mass number (A) of a nucleus is equal to:**
- a) #protons × #neutrons
- b) #protons + #neutrons
- c) #protons − #neutrons
- d) #neutrons only
- **Answer:** b) #protons + #neutrons
**Explanation:** Mass number is the sum of protons and neutrons in the nucleus[6].
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Here are 20 more multiple choice questions on general properties of nuclei with explained answers:
1. The mass M(N, Z) of a nucleus with N neutrons and Z protons which have binding energy B is given by:
- a) $$M = N m_n + Z m_p - \frac{B}{c^2}$$
- b) $$M = N m_n + Z m_p + \frac{B}{c^2}$$
- c) $$M = N m_n + Z m_p - B c^2$$
- d) $$M = N m_n + Z m_p + B c^2$$
- **Answer:** a) $$M = N m_n + Z m_p - \frac{B}{c^2}$$
**Explanation:** The mass of the nucleus equals the sum of the masses of protons and neutrons minus the mass equivalent of the binding energy (mass defect) [1].
2. A radioactive nucleus with initial atomic number Z and mass number A emits 2 alpha particles and 2 positrons. The ratio of neutrons to protons in the final nucleus is:
- a) $$\frac{A - Z - 4}{Z - 2}$$
- b) $$\frac{A - Z - 2}{Z - 6}$$
- c) $$\frac{A - Z - 4}{Z - 6}$$
- **Answer:** a) $$\frac{A - Z - 4}{Z - 2}$$
**Explanation:** Emission of 2 alphas reduces mass by 8 and protons by 4; 2 positrons reduce protons by 2, changing neutron-proton ratio accordingly [1].
3. The nuclear force is:
- a) Attractive between protons and neutrons
- b) Repulsive between protons and neutrons
- c) Attraction between protons and electrons
- d) Attraction between electrons and neutrons
- **Answer:** a) Attractive between protons and neutrons
**Explanation:** Nuclear force holds nucleons together inside the nucleus strongly [3].
4. The nuclear force is:
- a) Dependent on charge
- b) Weaker than electromagnetic
- c) Independent of charge
- d) Weaker than gravitational
- **Answer:** c) Independent of charge
**Explanation:** It acts equally among neutron-neutron, proton-proton, and neutron-proton irrespective of their charge [3].
5. The energy released in a nuclear reaction is called:
- a) R-value
- b) Q-value
- c) P-value
- d) Nuclear energy
- **Answer:** b) Q-value
**Explanation:** The Q-value represents the net energy released due to mass defect in nuclear reactions [3].
6. The nuclear force range is approximately:
- a) 1 meter
- b) 1 nanometer
- c) $$10^{-15}$$ meters (1 femtometer)
- d) Infinite
- **Answer:** c) $$10^{-15}$$ meters
**Explanation:** The force operates only over very short distances, about 1 fm [3].
7. In nuclear fission of uranium-235, a typical main product is:
- a) Helium
- b) Krypton
- c) Barium
- d) Oxygen
- **Answer:** c) Barium
**Explanation:** Fission fragments commonly include Barium and Krypton isotopes [3].
8. A neutron decays into a proton because:
- a) Neutron is lighter
- b) Proton is lighter
- c) Both are equally massive
- d) Neutron has positive charge
- **Answer:** b) Proton is lighter
**Explanation:** Conversion from neutron to proton releases energy due to proton's lower mass [2].
9. The half-life of a radioactive element is 30 minutes. The fraction remaining after 90 minutes is:
- a) 1/2
- b) 1/3
- c) 1/4
- d) 1/8
- **Answer:** d) 1/8
**Explanation:** After 3 half-lives, $$ (1/2)^3 = 1/8 $$ remains [2].
10. A nucleus losing a beta particle increases its atomic number by:
- a) 1
- b) 0
- c) -1
- d) 2
- **Answer:** a) 1
**Explanation:** Beta decay converts neutron to proton raising atomic number by 1 [6].
11. Isotope with no neutron is:
- a) Deuterium
- b) Tritium
- c) Protium (Hydrogen-1)
- d) Helium-3
- **Answer:** c) Protium
**Explanation:** Protium has one proton and zero neutrons [10].
12. Magic numbers in nuclear physics correspond to:
- a) Stable electron numbers
- b) Stable nucleon numbers
- c) Radioactive decay constants
- d) Binding energy peaks
- **Answer:** b) Stable nucleon numbers
**Explanation:** Magic numbers represent number of protons or neutrons that confer extra stability [11].
13. The energy required to remove a nucleon is:
- a) Ionization energy
- b) Binding energy
- c) Fission energy
- d) Coulomb energy
- **Answer:** b) Binding energy
**Explanation:** Binding energy keeps nucleons bound inside nucleus [6].
14. Density of nuclei is approximately:
- a) $$10^3 \text{ kg/m}^3$$
- b) $$10^{10} \text{ kg/m}^3$$
- c) $$10^{17} \text{ kg/m}^3$$
- d) Variable per element
- **Answer:** c) $$10^{17} \text{ kg/m}^3$$
**Explanation:** Nuclear matter is extremely dense [12].
15. Mass number (A) equals:
- a) Number of protons only
- b) Number of neutrons only
- c) Protons + neutrons
- d) Electrons + protons
- **Answer:** c) Protons + neutrons
**Explanation:** Mass number is total nucleon count [6].
16. A nucleus with odd mass number generally has:
- a) Integer spin
- b) Half-integer spin
- c) Zero spin
- d) No spin
- **Answer:** b) Half-integer spin
**Explanation:** Odd nucleon count leads to half-integer spin due to unpaired nucleon [13].
17. The nucleus has a diameter roughly:
- a) $$10^{-10} \text{ m}$$
- b) $$10^{-15} \text{ m}$$
- c) $$10^{-8} \text{ m}$$
- d) $$10^{-20} \text{ m}$$
- **Answer:** b) $$10^{-15} \text{ m}$$
**Explanation:** Nucleus size is about a few femtometers [14].
18. The binding energy per nucleon peaks around which element?
- a) Hydrogen
- b) Iron
- c) Uranium
- d) Lead
- **Answer:** b) Iron
**Explanation:** Iron has highest stability and binding energy per nucleon [15].
19. Charge of neutron is:
- a) +1 e
- b) 0
- c) -1 e
- d) +2 e
- **Answer:** b) 0
**Explanation:** Neutron is electrically neutral [13].
20. Nuclear reactions differ from chemical reactions because:
- a) They involve electrons
- b) They involve nucleons
- c) Mass is conserved exactly
- d) No energy is released
- **Answer:** b) They involve nucleons
**Explanation:** Nuclear reactions involve changes inside the nucleus, unlike chemical reactions which involve electrons [6].
