15.3 Nuclear Physics

• What is the focus of nuclear physics as compared to atomic physics?

  Structure of atomic nuclei
• Nuclear physics studies strong and weak nuclear forces
• Nuclear decay and nuclear reactions are key concepts in nuclear physics.

  True
• What are the particles found in the nucleus called collectively?

  Nucleons
• Protons and neutrons are bound together by the strong nuclear force
• Match the particle with its properties:

  Proton ↔️ +1 charge, 1 amu

  Neutron ↔️ 0 charge, 1 amu
• Neutrons contribute to the stability of the nucleus.

  True
• What are isotopes of an element?

  Same protons, different neutrons
• Isotopes have the same atomic number but different mass numbers.
• The atomic mass of an element is the weighted average of its isotopes' masses.

  True
• What symbol represents the atomic mass of an element?

  $\bar{m}$
• Radioactive decay is the process by which unstable nuclei lose energy by emitting particles.
• Alpha decay results in a decrease of the mass number by 4.


  True
• Match the type of decay with its emitted particle:

  Alpha decay ↔️ $\alpha$ particle

  Beta decay ↔️ $\beta$ particle

  Gamma decay ↔️ $\gamma$ rays
• What particle is emitted during alpha decay?

  $\alpha$ particle
• What are the two types of particles in the nucleus of an atom?

  Protons and neutrons
• Protons and neutrons are collectively known as nucleons
• The strong nuclear force binds nucleons together in the nucleus.


  True
• What determines the atomic number of an element?

  Number of protons
• Neutrons contribute to the stability of the nucleus.


  True
• What are isotopes of an element?

  Same protons, different neutrons
• Isotopes have the same atomic number but different mass
• The atomic mass of an element is the weighted average of its isotopes.


  True
• What is half-life in radioactive decay?

  Time for half nuclei to decay
• The decay constant is related to half-life by the formula $\lambda =$$\frac{\ln 2}{t_{1 / 2}}$, where t_{1 / 2}</latex> represents the half-life
• The decay constant measures the probability of a nucleus decaying per unit time.


  True
• What formula is used to calculate the remaining amount of a substance after $n$ half-lives?


  $N =$$N_{0} \left(\frac{1}{2}\right)^{n}$
• Match the conserved quantities in nuclear equations with their symbols:

  Mass Number ↔️ A

  Atomic Number ↔️ Z
• What must be conserved when balancing nuclear equations?

  Mass number and atomic number
• In the alpha decay of Uranium-238, the balanced nuclear equation is $_{92}^{238}U \rightarrow _{90}^{234}Th +$$_{2}^{4}He$, where $_{2}^{4}He$ represents an alpha particle.
• In the alpha decay of Uranium-238, both the mass number and atomic number are conserved.

  True
• What is binding energy in nuclear reactions?

  Energy to disassemble a nucleus
• Mass defect is the difference between the total mass of nucleons and the mass of the nucleus
• What is Einstein's equation relating energy and mass defect?

  $E =$$mc^{2}$
• In the fusion reaction $_{1}^{2}H +$$_{1}^{3}H \rightarrow _{2}^{4}He +$$_{0}^{1}n$, the energy released is calculated using the mass defect and Einstein's equation.


  True
• What happens during nuclear fission?

  Nucleus splits into smaller nuclei
• A chain reaction in nuclear fission is triggered by neutrons
• Chain reactions in nuclear fission can be controlled or uncontrolled depending on neutron moderation.


  True
• A chain reaction is a self-sustaining series of nuclear fissions triggered by neutrons
• What happens to the nucleus of an atom during nuclear fission?

  It splits into smaller nuclei