Physics Chapter 13: Nuclei
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Questions and Answers

What happens to the nuclear force between nucleons as their distance exceeds a few femtometres?

  • It falls rapidly to zero. (correct)
  • It remains constant.
  • It becomes repulsive.
  • It increases significantly.

At what distance does the potential energy between two nucleons reach its minimum?

  • 1.0 fm
  • 0.5 fm
  • 0.8 fm (correct)
  • 1.5 fm

Which of the following statements about nuclear force is true?

  • It is stronger than the Coulomb force. (correct)
  • It varies significantly with distance.
  • It has a simple mathematical formulation.
  • It depends on the electric charge of nucleons.

What is the nature of the nuclear force for separations greater than 0.8 femtometres?

<p>Attractive (C)</p> Signup and view all the answers

Which particles experience approximately the same nuclear force?

<p>Neutron-neutron (C)</p> Signup and view all the answers

What significant discovery did A.H. Becquerel make in 1896?

<p>Radioactivity (C)</p> Signup and view all the answers

Which material was used by Becquerel to demonstrate radioactivity after exposure to visible light?

<p>Uranium-potassium sulphate (D)</p> Signup and view all the answers

What occurs in a nucleus during radioactive decay?

<p>The nucleus undergoes a transformation. (A)</p> Signup and view all the answers

What does the symbol Z represent in nuclear composition?

<p>Number of protons (A)</p> Signup and view all the answers

What is the mass number A calculated by?

<p>Z + N (A)</p> Signup and view all the answers

What distinguishes isotopes of the same element?

<p>Different numbers of neutrons (A)</p> Signup and view all the answers

Which of the following pairs are considered isobars?

<p>13 H and 32 He (C)</p> Signup and view all the answers

What term describes the number of nucleons in an atom?

<p>Mass number A (A)</p> Signup and view all the answers

Which event established the existence of the atomic nucleus?

<p>Rutherford's gold foil experiment (D)</p> Signup and view all the answers

Which of the following statements is true about isotones?

<p>They have the same number of neutrons but different protons (D)</p> Signup and view all the answers

What is the approximate distance of closest approach to a gold nucleus by an alpha particle with kinetic energy of 5.5 MeV?

<p>4.0 × 10–14 m (D)</p> Signup and view all the answers

What does the atomic number Z represent in an atomic nucleus?

<p>The number of protons in the nucleus (B)</p> Signup and view all the answers

What is the relationship between mass number A, atomic number Z, and the number of neutrons N in a nucleus?

<p>A = Z + N (C)</p> Signup and view all the answers

Which term refers to nuclides that have the same mass number A but different atomic numbers Z?

<p>Isobars (C)</p> Signup and view all the answers

How is nuclear density described according to the content?

<p>It is independent of the mass number A (B)</p> Signup and view all the answers

What is the formula for calculating the nuclear radius R?

<p>R = R0 A^{1/3} (D)</p> Signup and view all the answers

What does the binding energy DEb of a nucleus represent?

<p>The energy required to separate nucleons (D)</p> Signup and view all the answers

What is the approximate binding energy per nucleon for nuclei with a mass number range A = 30 to 170?

<p>8 MeV/nucleon (B)</p> Signup and view all the answers

What is the energy equivalent of the mass defect DM in a nucleus expressed as?

<p>DEb = DM c^2 (B)</p> Signup and view all the answers

What happens to the difference in binding energies during a nuclear reaction?

<p>It is released or absorbed as energy. (D)</p> Signup and view all the answers

How does the mass defect in a chemical reaction compare to that in a nuclear reaction?

<p>It is almost a million times smaller. (B)</p> Signup and view all the answers

What is the definition of 1 atomic mass unit (1u)?

<p>1/12th mass of one atom of 12C. (D)</p> Signup and view all the answers

Why is there a general impression that mass-energy interconversion does not occur in chemical reactions?

<p>Chemical binding energy is negligible compared to nuclear binding energy. (D)</p> Signup and view all the answers

What is produced when a uranium isotope $^{235}_{92}U$ is bombarded with a neutron?

<p>Intermediate mass nuclear fragments (B)</p> Signup and view all the answers

What are the typical products of the fission of $^{235}_{92}U$?

<p>$^{120}<em>{51}Sb$ and $^{99}</em>{41}Nb$ (A), $^{144}<em>{56}Ba$ and $^{89}</em>{36}Kr$ (D)</p> Signup and view all the answers

What primarily contributes to the mass of an atom?

<p>The protons and neutrons in the nucleus. (A)</p> Signup and view all the answers

What is the charge of a nucleus?

<p>Positively charged. (D)</p> Signup and view all the answers

What is the approximate energy released per fissioning nucleus of uranium?

<p>200 MeV (D)</p> Signup and view all the answers

In terms of size, how does the radius of the nucleus compare to that of the atom?

<p>It is smaller by a factor of 10,000. (C)</p> Signup and view all the answers

In a fission reaction, what happens to the disintegration energy?

<p>It first appears as kinetic energy (B)</p> Signup and view all the answers

What happens to the radioactive nuclei produced from fission over time?

<p>They emit beta particles to achieve stability (B)</p> Signup and view all the answers

How does chemical binding energy relate to mass defect?

<p>It contributes negatively to mass, similar to nuclear reactions. (A)</p> Signup and view all the answers

What is one major difference between nuclear fission and nuclear fusion?

<p>Fusion releases more energy than fission (A), Fission occurs only in heavy elements (C)</p> Signup and view all the answers

How is the energy from fission utilized in nuclear reactors?

<p>By transferring it as heat to surrounding matter (A)</p> Signup and view all the answers

What is the relationship between binding energy and the stability of a nucleus?

<p>Higher binding energy indicates more stability (B)</p> Signup and view all the answers

What is the resulting element from the fusion reaction of 2.0 kg of deuterium?

<p>Helium-4 (D)</p> Signup and view all the answers

How much energy is released if all the atoms in 1 kg of pure 239Pu undergo fission?

<p>540 MeV (C)</p> Signup and view all the answers

What is the atomic mass of 13Al used in fission calculations?

<p>27.98191 u (A)</p> Signup and view all the answers

What is the relationship of nuclear matter density to mass number A?

<p>Density remains constant with A (B)</p> Signup and view all the answers

What is the potential barrier height during a head-on collision of two deuterons?

<p>2 fm (B)</p> Signup and view all the answers

What is the total atomic mass of combined 12C in the reaction producing 10Ne and 4He?

<p>24.0000 u (A)</p> Signup and view all the answers

What is the correct representation for the fusion reaction of deuterium?

<p>2H + 2H → 4He + n + 3.27 MeV (A)</p> Signup and view all the answers

Which fission reaction is energetically possible with 56Fe and 13Al?

<p>2(13Al) (B)</p> Signup and view all the answers

Flashcards

Atomic Number (Z)

The number of protons in an atom's nucleus.

Neutron Number (N)

The number of neutrons in an atom's nucleus.

Mass Number (A)

The total number of protons and neutrons in an atom's nucleus.

Nucleon

A proton or a neutron.

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Isotopes

Atoms of the same element with the same number of protons but different numbers of neutrons.

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Isobars

Nuclides (atoms) with the same mass number (A) but different atomic numbers (Z).

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Isotones

Nuclides with the same neutron number (N) but different atomic numbers (Z).

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Nuclide notation

A way to represent a specific nucleus using the atomic number (Z), mass number (A), and chemical symbol (X) in the format: ZA X

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Nuclear force strength

The nuclear force is significantly stronger than the Coulomb force and gravitational force.

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Nuclear force range

The nuclear force acts over a short range, rapidly decreasing to zero beyond a few femtometers.

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Saturation of nuclear forces

The nuclear force's strength in a large nucleus remains consistent.Binding energy per nucleon is nearly constant in larger nuclei.

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Nuclear potential energy

The energy between nucleons is minimum at a specific distance, indicating an attractive force at larger distances and a repulsive force at smaller distances.

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Nuclear force charge independence

The strength of the nuclear force between neutrons and neutrons, protons and neutrons, and protons and protons is similar; it doesn't change based on electric charge.

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Radioactivity

Unstable nuclei undergo decay, a nuclear phenomenon.

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Radioactive decay

The process of an unstable nucleus undergoing a decay.

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Becquerel's discovery

Becquerel accidentally discovered radioactivity while studying fluorescence and phosphorescence, observing penetrating radiation from uranium compounds.

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What is nuclear fission?

The process where a heavy nucleus splits into two or more lighter nuclei, releasing a huge amount of energy.

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Why is nuclear fission energy efficient?

The total binding energy of the resulting nuclei is greater than the original heavy nucleus, releasing energy due to the increased stability of the lighter nuclei.

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What are the products of fission?

The fission of a nucleus typically produces two intermediate-mass nuclei (fission fragments), neutrons, and a large amount of energy.

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Why are fission fragments radioactive?

The fission fragments are usually neutron-rich, making them unstable and radioactive. They undergo radioactive decay to reach a stable configuration.

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What is the Q-value of fission?

The energy released per fission event, typically around 200 MeV, which represents the difference in binding energy before and after fission.

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How is fission energy used?

Nuclear fission provides energy for nuclear power plants and also forms the basis of nuclear weapons.

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What is nuclear fusion?

The process where two lighter nuclei combine to form a heavier, more stable nucleus, releasing enormous energy.

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Why is fusion energy efficient?

Fusion releases a tremendous amount of energy because the resulting nucleus is more tightly bound than the original nuclei, as seen from the binding energy curve.

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Binding Energy Difference

The difference in binding energy between the reactants and products of a nuclear reaction determines whether energy is released or absorbed.

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Mass-Energy Interconversion

In a nuclear reaction, the difference in binding energy between the reactants and products manifests as a change in mass, demonstrating the equivalence of mass and energy.

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Chemical Reactions & Mass-Energy

Chemical reactions also involve mass-energy interconversion, but the differences in binding energy are much smaller than in nuclear reactions, making the mass changes nearly undetectable.

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Nuclear Reaction Energy

Nuclear reactions release or absorb a massive amount of energy due to the significant change in binding energy between the initial and final nuclei.

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Mass Defect

The difference between the actual mass of a nucleus and the sum of the masses of its individual protons and neutrons.

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Chemical Binding Energy

The energy holding atoms together in molecules, similar to nuclear binding energy but on a much smaller scale.

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Mass Defect in Chemical Reactions

The mass defect in chemical reactions is very small compared to nuclear reactions, making the mass-energy interconversion almost undetectable.

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Incorrect Impression of Mass-Energy in Chemical Reactions

The misconception that mass-energy interconversion doesn't occur in chemical reactions arises from the extremely small mass changes involved.

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What is mass defect?

The difference between the total mass of a nucleus's individual protons and neutrons and its actual measured mass.

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Binding energy

The energy required to completely break apart a nucleus into its individual protons and neutrons.

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How is binding energy related to mass defect?

The difference in mass between the nucleus and its components is converted into energy, representing the binding energy of the nucleus.

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What determines nuclear radius?

The radius of a nucleus is proportional to the cube root of its mass number (A), meaning larger nuclei have larger radii.

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Why is nuclear density constant?

The nuclear density is essentially independent of the nucleus’s size. This means that all nuclei have roughly the same density.

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What is the strong nuclear force?

A powerful, short-range force that holds protons and neutrons together inside the nucleus.

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What is a nuclide?

A specific type of atomic nucleus characterized by its unique number of protons and neutrons.

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What are isotopes?

Atoms of the same element that have the same number of protons but differ in the number of neutrons.

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Energy Released in Fission

The energy released during nuclear fission comes from the difference in binding energy between the initial heavy nucleus and the resulting lighter nuclei.

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Q-value of Fission

The Q-value represents the energy released per fission event, typically around 200 MeV. It's the difference in binding energy before and after fission.

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Fission Fragments

When a nucleus undergoes fission, it breaks into two or more intermediate-mass nuclei called fission fragments. These are usually neutron-rich and radioactive.

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Fusion Energy

Fusion reactions release enormous energy because the resulting heavier nucleus, formed from the fusion of two lighter nuclei, is more tightly bound, as seen from the binding energy curve.

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Deuterium-Tritium Fusion

The fusion reaction of deuterium and tritium produces helium and a neutron, releasing significant energy.

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Energy Released in Nuclear Reactions

Nuclear reactions release or absorb a massive amount of energy due to the significant change in binding energy between the initial and final nuclei.

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Study Notes

Chapter Thirteen: Nuclei

  • Nuclei are densely concentrated at the center of atoms, containing most of the atom's mass.
  • Nuclei are much smaller than the atom, approximately 10⁻¹² times smaller in volume.
  • Atomic nuclei contain protons and neutrons.
  • Atomic mass units (u) are used to measure small quantities on an atomic scale.
  • Isotopes are atoms of the same element differing in mass, sharing the same chemical properties.
  • Chlorine isotopes have masses of ~35 u and ~37 u, with ~75% and ~ 25% abundance respectively.
  • Hydrogen has 3 isotopes (protium, deuterium, and tritium) which differ in neutron numbers.
  • Protons have a positive charge and are stable
  • Neutrons have no charge and are stable within a nucleus but unstable outside.
  • Atomic number (Z) represents the number of protons.
  • Mass number (A) represents the total number of protons and neutrons.
  • A nucleus with the same mass number (A) but different atomic numbers (Z) are called isobars. A nucleus with the same number of neutrons (N) but different atomic number (Z) are called isotones.
  • Rutherford's experiments on alpha-particle scattering helped determine the size of a nucleus.
  • The radius of a nucleus is proportional to A^(1/3). Where A is the mass number.
  • Nuclear matter density is nearly constant, independent of atomic number (A)
  • Einstein’s mass-energy equivalence relation is fundamental to nuclear physics. (E = mc²).
  • Nuclear binding energy represents the energy required to separate a nucleus into its individual protons and neutrons.
  • The binding energy per nucleon is practically constant for mid-sized nuclei (30 < A < 170).
  • Nuclei with lower binding energy per nucleon (light and heavy) are less stable.
  • Fission involves heavy nuclei splitting into lighter nuclei, releasing energy. (e.g., Uranium- 235 fission)
  • Fusion involves light nuclei fusing to form heavier nuclei, releasing energy. (e.g., Hydrogen isotopes fusing to form Helium)
  • Radioactive decay: Nuclei emitting alpha (𝛼), beta (𝛽), and gamma (𝛾) particles.

Atomic Masses and Composition of Nucleus

  • The mass of an atom is very small compared to a kilogram e.g., the mass of a carbon-12 atom is 1.992647 x 10⁻²⁶ kg.
  • A more convenient unit (u/atomic mass unit) is used, defined as 1/12th the mass of a carbon-12 atom.

Mass-Energy and Nuclear Binding Energy

  • Mass and energy are interchangeable, according to Einstein's theory.
  • Mass defect is the difference between the mass of a nucleus and the sum of its constituent particles' masses.
  • This difference in mass is converted to binding energy.
  • Binding energy is crucial for holding the nucleus together.

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Explore the fundamental concepts of atomic nuclei in this quiz. Learn about the composition of nuclei, isotopes, atomic mass units, and the significance of protons and neutrons. Test your understanding of key terms and their applications in atomic physics.

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