Chapter 21

Define \(A, Z,\) and \(X\) in the following notation used to specify a nuclide: \({ }_{Z} \mathrm{X}\)

What is an alpha particle? What happens to the mass number and atomic number of a nuclide that emits an alpha particle?

What is a beta particle? What happens to the mass number and atomic number of a nuclide that emits a beta particle?

What is a gamma ray? What happens to the mass number and atomic number of a nuclide that emits a gamma ray?

What is a positron? What happens to the mass number and atomic number of a nuclide that emits a positron?

Describe the process of electron capture. What happens to the mass number and atomic number of a nuclide that undergoes electron capture?

Rank alpha particles, beta particles, positrons, and gamma rays in terms of: (a) increasing ionizing power; (b) increasing penetrating power.

Explain why the ratio of neutrons to protons \((N / Z)\) is important in determining nuclear stability. How can you use the \(N / Z\) ratio of a nuclide to predict the kind of radioactive decay that it might undergo?

Describe the basic way that each device detects radioactivity: (a) thermoluminescent dosimeter; (b) Geiger-Müller counter; and (c) scintillation counter.

Explain the concept of half-life with respect to radioactive nuclides. What rate law is characteristic of radioactivity?

Explain the main concepts behind the technique of radiocarbon dating. How can radiocarbon dating be corrected for changes in atmospheric concentrations of \(\mathrm{C}-14\) ? What range of ages can be reliably determined by C-14 dating?

Describe fission. Include the concepts of chain reaction and critical mass in your description. How and by whom was fission discovered? Explain how fission can be used to generate electricity.

What was the Manhattan Project? Briefly describe its development and culmination.

Describe the advantages and disadvantages of using fission to generate electricity.

Explain the concepts of mass defect and nuclear binding energy. At what mass number does the nuclear binding energy per nucleon peak? What is the significance of this?

What is fusion? Why can fusion and fission both produce energy? Explain.

What are some of the problems associated with using fusion to generate electricity?

Explain transmutation and provide one or two examples.

Explain the basic principles of cyclotron function.

Explain why different kinds of radiation affect biological tissues differently, even though the amount of radiation exposure may be the same.

Explain the significance of the biological effectiveness factor in measuring radiation exposure. What types of radiation would you expect to have the highest biological effectiveness factor?

Write a nuclear equation for the indicated decay of each nuclide. MISSED THIS? a. U-234 (alpha) b. Th- 230 (alpha) c. \(\mathrm{Pb}-214\) (beta) d. \(\mathrm{N}-13\) (positron emission) e. Cr-51 (electron capture)

Write a nuclear equation for the indicated decay of each nuclide. a. Po- 210 (alpha) b. Ac- 227 (beta) c. T1-207 (beta) d. O-15 (positron emission) e. Pd-103 (electron capture)

Write a partial decay series for Th- 232 undergoing the sequential decays: \(\alpha, \beta, \beta, \alpha\)

Write a partial decay series for Rn- 220 undergoing the sequential decays: \(\alpha, \alpha, \beta, \beta\)

Determine whether or not each nuclide is likely to be stable. State your reasons. MISSED THIS? a. \(\mathrm{Mg}-26\) b. \(\mathrm{Ne}-25\) c. \(\mathrm{Co}-51\) d. Te-124

One of the nuclides in spent nuclear fuel is U-235, an alpha emitter with a half-life of 703 million years. How long will it take for the amount of U-235 to reach \(10.0 \%\) of its initial amount?

A patient is given \(0.050 \mu \mathrm{g}\) of technetium-99m, a radioactive isotope with a half-life of about 6.0 hours. How long does it take for the radioactive isotope to decay to \(1.0 \times 10^{-3} \mu \mathrm{g}\) ? (Assume no excretion of the nuclide from the body.)

A radioactive sample contains \(1.55 \mathrm{~g}\) of an isotope with a halflife of 3.8 days. What mass of the isotope remains after 5.5 days?

At 8: 00 A.M., a patient receives a 1.5 - \(\mu\) g dose of \(I\) - 131 to treat thyroid cancer. If the nuclide has a half-life of eight days, what mass of the nuclide remains in the patient at \(5: 00 \mathrm{P}\). M. the next day? (Assume no excretion of the nuclide from the body.)

A sample of \(\mathrm{F}-18\) has an initial decay rate of \(1.5 \times 10^{5} / \mathrm{s}\). How long will it take for the decay rate to fall to \(2.5 \times 10^{3} / \mathrm{s}\) ? (F-18 has a half-life of 1.83 hours.)

A sample of T1-201 has an initial decay rate of \(5.88 \times 10^{4} / \mathrm{s}\). How long will it take for the decay rate to fall to \(287 / \mathrm{s} ?\) (T1-201 has a half-life of 3.042 days. \()\)

An ancient skull has a carbon- 14 decay rate of 0.85 disintegration per minute per gram of carbon \((0.85\) dis \(/ \min \cdot \mathrm{g} \mathrm{C})\). How old is the skull? (Assume that living organisms have a carbon-14 decay rate of 15.3 dis \(/ \mathrm{min} \cdot \mathrm{g} \mathrm{C}\) and that carbon- 14 has a half-life of 5715 yr. \()\)

Write the nuclear equation for the fusion of two \(\mathrm{H}-2\) atoms to form He- 3 and one neutron. MISSED THIS?

Write the nuclear equation for the fusion of \(\mathrm{H}-3\) with \(\mathrm{H}-1\) to form He-4.

A breeder nuclear reactor is a reactor in which nonfissionable (nonfissile) U-238 is converted into fissionable (fissile) Pu-239. The process involves bombardment of U-238 by neutrons to form U-239, which then undergoes two sequential beta decays. Write nuclear equations for this process.

Write the series of nuclear equations to represent the bombardment of Al- 27 with a neutron to form a product that subsequently undergoes a beta decay.

Rutherfordium-257 was synthesized by bombarding Cf-249 with C-12. Write the nuclear equation for this reaction.

Element 107 , now named bohrium, was synthesized by German researchers by colliding bismuth- 209 with chromium-54 to form a bohrium isotope and one neutron. Write the nuclear equation to represent this reaction.

PET studies require fluorine-18, which is produced in a cyclotron and decays with a half-life of 1.83 hours. Assuming that the \(\mathrm{F}-18\) can be transported at \(60.0 \mathrm{miles} /\) hour, how close must the hospital be to the cyclotron if \(65 \%\) of the \(\mathrm{F}-18\) produced makes it to the hospital?

Given that the energy released in the fusion of two deuterons to a \({ }^{3}\) He and a neutron is \(3.3 \mathrm{MeV}\), and in the fusion to tritium and a proton it is \(4.0 \mathrm{MeV},\) calculate the energy change for the process \({ }^{3} \mathrm{He}+{ }^{1} \mathrm{n} \longrightarrow{ }^{3} \mathrm{H}+{ }^{1} \mathrm{p} .\) Suggest an explanation for why this process occurs at much lower temperatures than either of the first two.

Approximately how many half-lives must pass for the amount of radioactivity in a substance to decrease to below \(1 \%\) of its initial level?

Have each group member study a different mode of radioactive decay (alpha, beta, gamma, positron emission, or electron capture) and present it to the group. Each presentation should include a description of the process, a description of how the atomic and mass numbers change, and at least one specific example. Presentations should also address the questions: What do all nuclear reactions have in common, and how do they differ from each other?

Radon-220 undergoes alpha decay with a half-life of \(55.6 \mathrm{~s}\). Assume there are 16,000 atoms present initially and make a table showing how many atoms will be present at \(0 \mathrm{~s}, 55.6 \mathrm{~s}, 111.2 \mathrm{~s}\), \(166.8 \mathrm{~s}, 222.4 \mathrm{~s},\) and \(278.0 \mathrm{~s}\) (all multiples of the half-life). Now calculate how many atoms will be present at \(50 \mathrm{~s}, 100 \mathrm{~s},\) and \(200 \mathrm{~s}\) (not multiples of the half-life). Make a graph with number of atoms present on the \(y\) -axis and total time on the \(x\) -axis.