Nucleon Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. What is meant by a nucleon?

Ans. A nucleon is a proton or a neutron considered in its role as a component of an atomic nucleus in physics and chemistry. The number of nucleons in a nucleus determines the mass number (nucleon number) of an atom.

Ques. A free neutron decays into a proton but a free proton does not decay into a neutron. This is because

1. neutron is an uncharged particle
2. neutron has a larger rest mass than a proton
3. neutron is a composite particle made of a proton and an electron
4. proton is a charged particle

Ans. The correct answer is b. neutron has a larger rest mass than a proton

Explanation: Because a neutron has a greater rest mass than a proton, decaying a proton into a neutron will require energy.

Ques. What is an atomic nucleus?

Ans. An atomic nucleus is a small, dense area of protons and neutrons at the center of an atom. Ernest Rutherford discovered the atomic nucleus in 1911 based on the 1909 Geiger-Marsden gold foil experiment.

Ques. Protons and neutrons are integral parts of an atomic nucleus as they cannot survive _________.

Ans. Independently

Explanation: Protons and neutrons cannot survive independently. They are the integral parts of an atomic nucleus.

Ques. What is the difference between a Nucleon and a Nucleus?

Ans. A nucleon is a subatomic particle of the atomic nucleus that is either a proton or a neutron, whereas the nucleus is the core, the central component of the atomic nucleus that stays together.

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Short Answers Questions [2 Marks Questions]

Ques. Explain with an example, whether the neutron to proton ratio in a nucleus increases or decreases due to β-decay.

Ans. The neutron-to-proton ratio of an atom nucleus is the number of neutrons divided by the number of protons. In a stable nucleus, this ratio normally increases with increasing atomic number.

The ratio of neutron to proton decreases due to Beta decay. For example

C₆¹⁴ → N₇¹⁴ + e^-

Ques. What is the binding energy per nucleon?

Ans. Nuclei are made up of protons and neutrons, however, the mass of the nucleus is less than the total of the individual masses of the neutrons and protons. The difference is the amount of binding energy per nucleon that holds the nucleons together. The Einstein relation may be utilized in calculating this energy:

Nuclear binding energy, E = mc²

For alpha particles, Δm = 0.0304 u and has a binding energy of E = 28.3 MeV.

Ques. What is a quark?

Ans. Before the 1960s, nucleons were thought to be the most fundamental elementary particles, as they were not made up of smaller parts. They are currently known as "composite particles" because they are made up of three quarks confined together by a strong interaction. Nuclear force or internucleon interaction is the interaction between many nucleons that is finally produced through the strong interaction.

Ques. What are the types of nucleons?

Ans. Protons and neutrons are the two types of nucleons. Electrons are negatively charged subatomic particles, whereas protons are positively charged subatomic particles. A strong nuclear force holds all protons together in any nucleus. 

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Long Answers Questions [3 Marks Questions]

Ques. Describe the types of quarks and establish relationships among them.

Ans. Quarks are classified into six categories. Another name for Quark is Flavour. Hence, there are six types of flavours

• Up
• Down
• Charm
• Strange
• Top
• Bottom

These six flavours are found in three pairs. These are

• Up and down flavours
• Charm and strange flavours
• Top and bottom flavours

Two of these six quarks, up and down, are the most stable and lightest in weight. The remaining four flavours are heavier and more unstable in nature, and they tend to convert quickly to up and down quarks during the particle decay process.

Ques. A radioactive nuclide decays to form a stable nuclide. Its half-life is 3 minutes. What fraction of its 1 g will remain radioactive after 9 minutes?

Ans. Let the number of atoms per gram = N₀

Given

• Half-life, T = 3 minutes
• Time after the fraction of 1 g remains radioactive, t = 9 minutes

The number of atoms that remain undecayed after 9 minutes is given by

N/N₀ = (1/2)^t/T = (1/2)^9/3 = (1/2)³ = 1/8 

⇒ N = N₀/8 

Therefore, in 9 minutes 1/8 part of N₀ remain undecayed i.e. 0.125.

Ques. Define binding energy per nucleon. What are its significance?

Ans. The average energy required to release a nuleon from a nucleus is called binding energy per nucleon. It is given by

Binding energy per nucleon = Binding energy / mass number

Binding energy per nucleon determines the stability of a nucleus. If the it is less then the nucleus is stable whereas the nucleus is more stable if its binding energy per nucleon is higher.

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Very Long Answers Questions [5 Marks Questions]

Ques. What are the main characteristics of nucleons?

Ans. Neutrons are not stable on their own, but they may be found in nuclear processes and utilized in scientific research. 

• The proton and neutron are both made up of three quarks. 
• A proton has two up quarks (the lightest of all quarks, a primary component of matter, and a type of fundamental particle), while a neutron contains one up quark and two down quarks. 
• They are an essential component of the atomic nucleus since they cannot exist as separate nucleons. 
• Nucleons are composite particles made up of three quarks that are held together by a strong interaction. 
• The nucleons are held tightly together by the atomic nucleus. 
• When the force is broken, it may create a lot of power, which is known as nuclear energy, and it is comparable to what is used in nuclear weapons. 
• Nucleons found in radioactive decay compounds such as uranium can be dangerous because they can spread alpha radiation in just a matter of seconds.

Ques. What are the properties of nuclear forces?

Ans. The properties of nuclear forces are

• The nature of the nuclear force is attractive but it has a repulsive core. That is why the nucleus is maintained together without collapsing in on itself.
• It has an attractive exterior but a disgusting core. That is why the nucleus is maintained together without collapsing in on itself.
• The nuclear force is a short-range force. 
• The gap between particles in a nucleus is extremely small at 1 Fermi. 
• The nuclear force is far stronger than the repulsive Coulomb's force that causes the particles away at this range. If the distance is more than 2.5 Fermi, nuclear force is basically non-existent.
• All nucleons have the same nuclear force. If the Coulomb barrier is taken into account, nuclear force affects everything the same way, whether it is a neutron or a proton.
• The nuclear force is an exchange force.
• It is a non-central force.

Ques. Calculate the binding energy of ₈O¹⁶ nucleus. Given

1. The mass of ₈O¹⁶ = 15.994914 amu
2. Mass of proton = 1.007825 amu
3. Mass of neutron = 1.008665 amu

Ans. ₈O¹⁶ contains 8 protons and 8 neutrons.

Given

• The mass of ₈O¹⁶, M= 15.994914 amu
• Mass of proton, m_p = 1.007825 amu
• Mass of neutron, m_n = 1.008665 amu

The mass of the constituents of ₈O¹⁶ nucleus is given by

M’ = 8m_n + 8m_p

⇒ M’ = 8(m_n + m_p)

⇒ M’ = 8(1.00866 + 1.007825) = 16.13192 amu

Mass defect is given by

Δm = mass of the constituents of the nucleus - mass of the nucleus

⇒ Δm = 16.13192 - 15.994914 = 0.137 amu

Therefore, the binding energy of ₈O¹⁶ nucleus is given by

E = Δm x 931 MeV

⇒ E = 0.137 x 931 = 127.55 MeV

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