Key Terms, Key Equations, Summaries, and Exercises (Chapter 20)

OpenStax

Private: Chapter Twenty

Key Terms, Key Equations, Summaries, and Exercises (Chapter 20)

Key Terms

alpha (α) decay: loss of an alpha particle during radioactive decay

alpha particle: [latex]\left(\alpha \text { or }{ }_{2}^{4} \mathrm{He} \text { or }{ }_{2}^{4} \boldsymbol{\alpha}\right)[/latex] high-energy helium nucleus; a helium atom that has lost two electrons and contains two protons and two neutrons

antimatter: particles with the same mass but opposite properties (such as charge) of ordinary particles

band of stability: (also, belt of stability, zone of stability, or valley of stability) region of graph of number of protons versus number of neutrons containing stable (nonradioactive) nuclides

becquerel (Bq): SI unit for rate of radioactive decay; 1 Bq = 1 disintegration/s

beta (β) decay: breakdown of a neutron into a proton, which remains in the nucleus, and an electron, which is emitted as a beta particle

beta particle

[latex]\left(\beta \text { or }{ }_{-1}^{0} \mathrm{e} \text { or }{ }_{-1}^{0} \boldsymbol{\beta}\right)[/latex] high-energy electron

binding energy per nucleon: total binding energy for the nucleus divided by the number of nucleons in the nucleus

chain reaction: repeated fission caused when the neutrons released in fission bombard other atoms

chemotherapy: similar to internal radiation therapy, but chemical rather than radioactive substances are introduced into the body to kill cancer cells

containment system: (also, shield) a three-part structure of materials that protects the exterior of a nuclear fission reactor and operating personnel from the high temperatures, pressures, and radiation levels inside the reactor

control rod: material inserted into the fuel assembly that absorbs neutrons and can be raised or lowered to adjust the rate of a fission reaction

critical mass: amount of fissionable material that will support a self-sustaining (nuclear fission) chain reaction

curie (Ci): larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7 10¹⁰ disintegrations/s

daughter nuclide: nuclide produced by the radioactive decay of another nuclide; may be stable or may decay further

electron capture: combination of a core electron with a proton to yield a neutron within the nucleus

electron volt (eV): measurement unit of nuclear binding energies, with 1 eV equaling the amount energy due to the moving an electron across an electric potential difference of 1 volt

external beam radiation therapy: radiation delivered by a machine outside the body

fissile (or fissionable): when a material is capable of sustaining a nuclear fission reaction

fission: splitting of a heavier nucleus into two or more lighter nuclei, usually accompanied by the conversion of mass into large amounts of energy

fusion: combination of very light nuclei into heavier nuclei, accompanied by the conversion of mass into large amounts of energy

fusion reactor: nuclear reactor in which fusion reactions of light nuclei are controlled

gamma (γ) emission: decay of an excited-state nuclide accompanied by emission of a gamma ray

gamma ray

[latex](\gamma \text { or } {}_{0}^{0} \gamma) short wavelength, high-energy electromagnetic radiation that exhibits wave-particle duality

Geiger counter: instrument that detects and measures radiation via the ionization produced in a Geiger-Müller tube

gray (Gy): SI unit for measuring radiation dose; 1 Gy = 1 J absorbed/kg tissue

half-life (t_1/2): time required for half of the atoms in a radioactive sample to decay

internal radiation therapy: (also, brachytherapy) radiation from a radioactive substance introduced into the body to kill cancer cells

ionizing radiation: radiation that can cause a molecule to lose an electron and form an ion

magic number: nuclei with specific numbers of nucleons that are within the band of stability

mass defect: difference between the mass of an atom and the summed mass of its constituent subatomic particles (or the mass “lost” when nucleons are brought together to form a nucleus)

mass-energy equivalence equation: Albert Einstein’s relationship showing that mass and energy are equivalent

millicurie (mCi): larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7 $\times "> \times$ 10¹⁰ disintegrations/s

nonionizing radiation: radiation that speeds up the movement of atoms and molecules; it is equivalent to heating a sample, but is not energetic enough to cause the ionization of molecules

nuclear binding energy: energy lost when an atom’s nucleons are bound together (or the energy needed to break a nucleus into its constituent protons and neutrons)

nuclear chemistry: study of the structure of atomic nuclei and processes that change nuclear structure

nuclear fuel: fissionable isotope present in sufficient quantities to provide a self-sustaining chain reaction in a nuclear reactor

nuclear moderator: substance that slows neutrons to a speed low enough to cause fission

nuclear reaction: change to a nucleus resulting in changes in the atomic number, mass number, or energy state

nuclear reactor: environment that produces energy via nuclear fission in which the chain reaction is controlled and sustained without explosion

nuclear transmutation: conversion of one nuclide into another nuclide

nucleon: collective term for protons and neutrons in a nucleus

nuclide: nucleus of a particular isotope

parent nuclide: unstable nuclide that changes spontaneously into another (daughter) nuclide

particle accelerator: device that uses electric and magnetic fields to increase the kinetic energy of nuclei used in transmutation reactions

positron

[latex]\left({ }_{+1}^{0} \beta \text { or }_{+1}^{0} \mathrm{e}\right)[/latex] antiparticle to the electron; it has identical properties to an electron, except for having the opposite (positive) charge

positron emission: (also, β⁺ decay) conversion of a proton into a neutron, which remains in the nucleus, and a positron, which is emitted

radiation absorbed dose (rad): SI unit for measuring radiation dose, frequently used in medical applications; 1 rad = 0.01 Gy

radiation dosimeter: device that measures ionizing radiation and is used to determine personal radiation exposure

radiation therapy: use of high-energy radiation to damage the DNA of cancer cells, which kills them or keeps them from dividing

radioactive decay: spontaneous decay of an unstable nuclide into another nuclide

radioactive decay series: chains of successive disintegrations (radioactive decays) that ultimately lead to a stable end-product

radioactive tracer: (also, radioactive label) radioisotope used to track or follow a substance by monitoring its radioactive emissions

radioactivity: phenomenon exhibited by an unstable nucleon that spontaneously undergoes change into a nucleon that is more stable; an unstable nucleon is said to be radioactive

radiocarbon dating: highly accurate means of dating objects 30,000–50,000 years old that were derived from once-living matter; achieved by calculating the ratio of ¹⁴₆C: ¹²₆C in the object vs. the ratio of ¹⁴₆C: ¹²₆C in the present-day atmosphere

radioisotope: isotope that is unstable and undergoes conversion into a different, more stable isotope

radiometric dating: use of radioisotopes and their properties to date the formation of objects such as archeological artifacts, formerly living organisms, or geological formations

reactor coolant: assembly used to carry the heat produced by fission in a reactor to an external boiler and turbine where it is transformed into electricity

relative biological effectiveness (RBE): measure of the relative damage done by radiation

roentgen equivalent man (rem): unit for radiation damage, frequently used in medicine; 100 rem = 1 Sv

scintillation counter: instrument that uses a scintillator—a material that emits light when excited by ionizing radiation—to detect and measure radiation

sievert (Sv): SI unit measuring tissue damage caused by radiation; takes into account energy and biological effects of radiation

strong nuclear force: force of attraction between nucleons that holds a nucleus together

subcritical mass: amount of fissionable material that cannot sustain a chain reaction; less than a critical mass

supercritical mass: amount of material in which there is an increasing rate of fission

transmutation reaction: bombardment of one type of nuclei with other nuclei or neutrons

transuranium element: element with an atomic number greater than 92; these elements do not occur in nature

Key Equations

E = mc²

decay rate = λN

[latex]t_{1 / 2}=\frac{\ln 2}{\lambda}=\frac{0.693}{\lambda}[/latex]

rem = RBE x rad

Sv = RBE x Gy

Summaries

20.1 Nuclear Structure and Stability

An atomic nucleus consists of protons and neutrons, collectively called nucleons. Although protons repel each other, the nucleus is held tightly together by a short-range, but very strong, force called the strong nuclear force. A nucleus has less mass than the total mass of its constituent nucleons. This “missing” mass is the mass defect, which has been converted into the binding energy that holds the nucleus together according to Einstein’s mass-energy equivalence equation, E = mc². Of the many nuclides that exist, only a small number are stable. Nuclides with even numbers of protons or neutrons, or those with magic numbers of nucleons, are especially likely to be stable. These stable nuclides occupy a narrow band of stability on a graph of number of protons versus number of neutrons. The binding energy per nucleon is largest for the elements with mass numbers near 56; these are the most stable nuclei.

20.2 Nuclear Equations

Nuclei can undergo reactions that change their number of protons, number of neutrons, or energy state. Many different particles can be involved in nuclear reactions. The most common are protons, neutrons, positrons (which are positively charged electrons), alpha (α) particles (which are high-energy helium nuclei), beta (β) particles (which are high-energy electrons), and gamma (γ) rays (which compose high-energy electromagnetic radiation). As with chemical reactions, nuclear reactions are always balanced. When a nuclear reaction occurs, the total mass (number) and the total charge remain unchanged.

20.3 Radioactive Decay

Nuclei that have unstable n:p ratios undergo spontaneous radioactive decay. The most common types of radioactivity are α decay, β decay, γ emission, positron emission, and electron capture. Nuclear reactions also often involve γ rays, and some nuclei decay by electron capture. Each of these modes of decay leads to the formation of a new nucleus with a more stable n:p ratio. Some substances undergo radioactive decay series, proceeding through multiple decays before ending in a stable isotope. All nuclear decay processes follow first-order kinetics, and each radioisotope has its own characteristic half-life, the time that is required for half of its atoms to decay. Because of the large differences in stability among nuclides, there is a very wide range of half-lives of radioactive substances. Many of these substances have found useful applications in medical diagnosis and treatment, determining the age of archaeological and geological objects, and more.

20.4 Transmutation and Nuclear Energy

It is possible to produce new atoms by bombarding other atoms with nuclei or high-speed particles. The products of these transmutation reactions can be stable or radioactive. A number of artificial elements, including technetium, astatine, and the transuranium elements, have been produced in this way.

Nuclear power as well as nuclear weapon detonations can be generated through fission (reactions in which a heavy nucleus is split into two or more lighter nuclei and several neutrons). Because the neutrons may induce additional fission reactions when they combine with other heavy nuclei, a chain reaction can result. Useful power is obtained if the fission process is carried out in a nuclear reactor. The conversion of light nuclei into heavier nuclei (fusion) also produces energy. At present, this energy has not been contained adequately and is too expensive to be feasible for commercial energy production.

20.5 Uses of Radioisotopes

Compounds known as radioactive tracers can be used to follow reactions, track the distribution of a substance, diagnose and treat medical conditions, and much more. Other radioactive substances are helpful for controlling pests, visualizing structures, providing fire warnings, and for many other applications. Hundreds of millions of nuclear medicine tests and procedures, using a wide variety of radioisotopes with relatively short half-lives, are performed every year in the US. Most of these radioisotopes have relatively short half-lives; some are short enough that the radioisotope must be made on-site at medical facilities. Radiation therapy uses high-energy radiation to kill cancer cells by damaging their DNA. The radiation used for this treatment may be delivered externally or internally.

20.6Biological Effects of Radiation

We are constantly exposed to radiation from a variety of naturally occurring and human-produced sources. This radiation can affect living organisms. Ionizing radiation is the most harmful because it can ionize molecules or break chemical bonds, which damages the molecule and causes malfunctions in cell processes. It can also create reactive hydroxyl radicals that damage biological molecules and disrupt physiological processes. Radiation can cause somatic or genetic damage, and is most harmful to rapidly reproducing cells. Types of radiation differ in their ability to penetrate material and damage tissue, with alpha particles the least penetrating but potentially most damaging and gamma rays the most penetrating.

Various devices, including Geiger counters, scintillators, and dosimeters, are used to detect and measure radiation, and monitor radiation exposure. We use several units to measure radiation: becquerels or curies for rates of radioactive decay; gray or rads for energy absorbed; and rems or sieverts for biological effects of radiation. Exposure to radiation can cause a wide range of health effects, from minor to severe, and including death. We can minimize the effects of radiation by shielding with dense materials such as lead, moving away from the source, and limiting time of exposure.

Exercises

20.1 Nuclear Structure and Stability

1.

Write the following isotopes in hyphenated form (e.g., “carbon-14”)

(a) $_{11}^{24} Na$

(b) $_{13}^{29} Al$

(c) $_{36}^{73} Kr$

(d) $_{77}^{194} Ir$

2.

Write the following isotopes in nuclide notation (e.g., $"_{6}^{14} C ")$

(a) oxygen-14

(b) copper-70

(c) tantalum-175

(d) francium-217

3.

For the following isotopes that have missing information, fill in the missing information to complete the notation

(a) $_{14}^{34} X$

(b) $_{X}^{36} P$

(c) $_{X}^{57} Mn$

(d) $_{56}^{121} X$

4.

For each of the isotopes in Exercise 20.1, determine the numbers of protons, neutrons, and electrons in a neutral atom of the isotope.

5.

Write the nuclide notation, including charge if applicable, for atoms with the following characteristics:

(a) 25 protons, 20 neutrons, 24 electrons

(b) 45 protons, 24 neutrons, 43 electrons

(c) 53 protons, 89 neutrons, 54 electrons

(d) 97 protons, 146 neutrons, 97 electrons

6.

Calculate the density of the $_{12}^{24} Mg$ nucleus in g/mL, assuming that it has the typical nuclear diameter of 1 $\times$ 10^–13 cm and is spherical in shape.

7.

What are the two principal differences between nuclear reactions and ordinary chemical changes?

8.

The mass of the atom $_{11}^{23} Na$ is 22.9898 amu.

(a) Calculate its binding energy per atom in millions of electron volts.

(b) Calculate its binding energy per nucleon.

9.

Which of the following nuclei lie within the band of stability shown in Figure 20.2?

(a) chlorine-37

(b) calcium-40

(c) ²⁰⁴Bi

(d) ⁵⁶Fe

(e) ²⁰⁶Pb

(f) ²¹¹Pb

(g) ²²²Rn

(h) carbon-14

10.

Which of the following nuclei lie within the band of stability shown in Figure 20.2?

(a) argon-40

(b) oxygen-16

(c) ¹²²Ba

(d) ⁵⁸Ni

(e) ²⁰⁵Tl

(f) ²¹⁰Tl

(g) ²²⁶Ra

(h) magnesium-24

20.2 Nuclear Equations

11.

Write a brief description or definition of each of the following:

(a) nucleon

(b) α particle

(c) β particle

(d) positron

(e) γ ray

(f) nuclide

(g) mass number

(h) atomic number

12.

Which of the various particles (α particles, β particles, and so on) that may be produced in a nuclear reaction are actually nuclei?

13.

Complete each of the following equations by adding the missing species:

(a) $_{13}^{27} Al +_{2}^{4} He ⟶ ? +_{0}^{1} n$

(b) $_{94}^{239} Pu + ? ⟶_{96}^{242} Cm +_{0}^{1} n$

(c) $_{7}^{14} N +_{2}^{4} He ⟶ ? +_{1}^{1} H$

(d) $_{92}^{235} U ⟶ ? +_{55}^{135} Cs + 4_{0}^{1} n$

14.

Complete each of the following equations:

(a) $_{3}^{7} Li + ? ⟶ 2_{2}^{4} He$

(b) $_{6}^{14} C ⟶_{7}^{14} N + ?$

(c) $_{13}^{27} Al +_{2}^{4} He ⟶ ? +_{0}^{1} n$

(d) $_{96}^{250} Cm ⟶ ? +_{38}^{98} Sr + 4_{0}^{1} n$

15.

Write a balanced equation for each of the following nuclear reactions:

(a) the production of ¹⁷O from ¹⁴N by α particle bombardment

(b) the production of ¹⁴C from ¹⁴N by neutron bombardment

(c) the production of ²³³Th from ²³²Th by neutron bombardment

(d) the production of ²³⁹U from ²³⁸U by $_{1}^{2} H$ bombardment

16.

Technetium-99 is prepared from ⁹⁸Mo. Molybdenum-98 combines with a neutron to give molybdenum-99, an unstable isotope that emits a β particle to yield an excited form of technetium-99, represented as ⁹⁹Tc^*. This excited nucleus relaxes to the ground state, represented as ⁹⁹Tc, by emitting a γ ray. The ground state of ⁹⁹Tc then emits a β particle. Write the equations for each of these nuclear reactions.

17.

The mass of the atom $_{9}^{19} F$ is 18.99840 amu.

(a) Calculate its binding energy per atom in millions of electron volts.

(b) Calculate its binding energy per nucleon.

18.

For the reaction $_{6}^{14} C ⟶_{7}^{14} N + ?,$ if 100.0 g of carbon reacts, what volume of nitrogen gas (N₂) is produced at 273K and 1 atm?

20.3 Radioactive Decay

19.

What are the types of radiation emitted by the nuclei of radioactive elements?

20.

What changes occur to the atomic number and mass of a nucleus during each of the following decay scenarios?

(a) an α particle is emitted

(b) a β particle is emitted

(c) γ radiation is emitted

(d) a positron is emitted

(e) an electron is captured

21.

What is the change in the nucleus that results from the following decay scenarios?

(a) emission of a β particle

(b) emission of a β⁺ particle

(c) capture of an electron

22.

Many nuclides with atomic numbers greater than 83 decay by processes such as electron emission. Explain the observation that the emissions from these unstable nuclides also normally include α particles.

23.

Why is electron capture accompanied by the emission of an X-ray?

24.

Explain, in terms of Figure 20.2, how unstable heavy nuclides (atomic number > 83) may decompose to form nuclides of greater stability (a) if they are below the band of stability and (b) if they are above the band of stability.

25.

Which of the following nuclei is most likely to decay by positron emission? Explain your choice.

(a) chromium-53

(b) manganese-51

(c) iron-59

26.

The following nuclei do not lie in the band of stability. How would they be expected to decay? Explain your answer.

(a) $_{15}^{34} P$

(b) $_{92}^{239} U$

(c) $_{20}^{38} Ca$

(d) $_{1}^{3} H$

(e) $_{94}^{245} Pu$

27.

The following nuclei do not lie in the band of stability. How would they be expected to decay?

(a) $_{15}^{28} P$

(b) $_{92}^{235} U$

(c) $_{20}^{37} Ca$

(d) $_{3}^{9} L i$

(e) $_{96}^{245} Cm$

28.

Predict by what mode(s) of spontaneous radioactive decay each of the following unstable isotopes might proceed:

(a) $_{2}^{6} H e$

(b) $_{30}^{60} Zn$

(c) $_{91}^{235} Pa$

(d) $_{94}^{241} Np$

(e) ¹⁸F

(f) ¹²⁹Ba

(g) ²³⁷Pu

29.

Write a nuclear reaction for each step in the formation of $_{84}^{218} Po$ from $_{98}^{238} U,$ which proceeds by a series of decay reactions involving the step-wise emission of α, β, β, α, α, α particles, in that order.

30.

Write a nuclear reaction for each step in the formation of $_{82}^{208} Pb$ from $_{90}^{228} T h,$ which proceeds by a series of decay reactions involving the step-wise emission of α, α, α, α, β, β, α particles, in that order.

31.

Define the term half-life and illustrate it with an example.

32.

A 1.00 $\times$ 10^–6-g sample of nobelium, $_{102}^{254} No,$ has a half-life of 55 seconds after it is formed. What is the percentage of $_{102}^{254} No$ remaining at the following times?

(a) 5.0 min after it forms

(b) 1.0 h after it forms

33.

²³⁹Pu is a nuclear waste byproduct with a half-life of 24,000 y. What fraction of the ²³⁹Pu present today will be present in 1000 y?

34.

The isotope ²⁰⁸Tl undergoes β decay with a half-life of 3.1 min.

(a) What isotope is produced by the decay?

(b) How long will it take for 99.0% of a sample of pure ²⁰⁸Tl to decay?

(c) What percentage of a sample of pure ²⁰⁸Tl remains un-decayed after 1.0 h?

35.

If 1.000 g of $_{88}^{226} Ra$ produces 0.0001 mL of the gas $_{86}^{222} Rn$ at STP (standard temperature and pressure) in 24 h, what is the half-life of ²²⁶Ra in years?

36.

The isotope $_{38}^{90} Sr$ is one of the extremely hazardous species in the residues from nuclear power generation. The strontium in a 0.500-g sample diminishes to 0.393 g in 10.0 y. Calculate the half-life.

37.

Technetium-99 is often used for assessing heart, liver, and lung damage because certain technetium compounds are absorbed by damaged tissues. It has a half-life of 6.0 h. Calculate the rate constant for the decay of $_{43}^{99} Tc .$

38.

What is the age of mummified primate skin that contains 8.25% of the original quantity of ¹⁴C?

39.

A sample of rock was found to contain 8.23 mg of rubidium-87 and 0.47 mg of strontium-87.

(a) Calculate the age of the rock if the half-life of the decay of rubidium by β emission is 4.7 $\times$ 10¹⁰ y.

(b) If some $_{38}^{87} Sr$ was initially present in the rock, would the rock be younger, older, or the same age as the age calculated in (a)? Explain your answer.

40.

A laboratory investigation shows that a sample of uranium ore contains 5.37 mg of $_{92}^{238} U$ and 2.52 mg of $_{82}^{206} Pb .$ Calculate the age of the ore. The half-life of $_{92}^{238} U$ is 4.5 $\times$ 10⁹ yr.

41.

Plutonium was detected in trace amounts in natural uranium deposits by Glenn Seaborg and his associates in 1941. They proposed that the source of this ²³⁹Pu was the capture of neutrons by ²³⁸U nuclei. Why is this plutonium not likely to have been trapped at the time the solar system formed 4.7 $\times$ 10⁹ years ago?

42.

A $_{4}^{7} Be$ atom (mass = 7.0169 amu) decays into a $_{3}^{7} L i$ atom (mass = 7.0160 amu) by electron capture. How much energy (in millions of electron volts, MeV) is produced by this reaction?

43.

A $_{5}^{8} B$ atom (mass = 8.0246 amu) decays into a $_{4}^{8} B$ atom (mass = 8.0053 amu) by loss of a β⁺ particle (mass = 0.00055 amu) or by electron capture. How much energy (in millions of electron volts) is produced by this reaction?

44.

Isotopes such as ²⁶Al (half-life: 7.2 $\times$ 10⁵ years) are believed to have been present in our solar system as it formed, but have since decayed and are now called extinct nuclides.

(a) ²⁶Al decays by β⁺ emission or electron capture. Write the equations for these two nuclear transformations.

(b) The earth was formed about 4.7 $\times$ 10⁹ (4.7 billion) years ago. How old was the earth when 99.999999% of the ²⁶Al originally present had decayed?

45.

Write a balanced equation for each of the following nuclear reactions:

(a) bismuth-212 decays into polonium-212

(b) beryllium-8 and a positron are produced by the decay of an unstable nucleus

(c) neptunium-239 forms from the reaction of uranium-238 with a neutron and then spontaneously converts into plutonium-239

(d) strontium-90 decays into yttrium-90

46.

Write a balanced equation for each of the following nuclear reactions:

(a) mercury-180 decays into platinum-176

(b) zirconium-90 and an electron are produced by the decay of an unstable nucleus

(c) thorium-232 decays and produces an alpha particle and a radium-228 nucleus, which decays into actinium-228 by beta decay

(d) neon-19 decays into fluorine-19

20.4 Transmutation and Nuclear Energy

47.

Write the balanced nuclear equation for the production of the following transuranium elements:

(a) berkelium-244, made by the reaction of Am-241 and He-4

(b) fermium-254, made by the reaction of Pu-239 with a large number of neutrons

(c) lawrencium-257, made by the reaction of Cf-250 and B-11

(d) dubnium-260, made by the reaction of Cf-249 and N-15

48.

How does nuclear fission differ from nuclear fusion? Why are both of these processes exothermic?

49.

Both fusion and fission are nuclear reactions. Why is a very high temperature required for fusion, but not for fission?

50.

Cite the conditions necessary for a nuclear chain reaction to take place. Explain how it can be controlled to produce energy, but not produce an explosion.

51.

Describe the components of a nuclear reactor.

52.

In usual practice, both a moderator and control rods are necessary to operate a nuclear chain reaction safely for the purpose of energy production. Cite the function of each and explain why both are necessary.

53.

Describe how the potential energy of uranium is converted into electrical energy in a nuclear power plant.

54.

The mass of a hydrogen atom $(_{1}^{1} H)$ is 1.007825 amu; that of a tritium atom $(_{1}^{3} H)$ is 3.01605 amu; and that of an α particle is 4.00150 amu. How much energy in kilojoules per mole of $_{2}^{4} He$ produced is released by the following fusion reaction: $_{1}^{1} H +_{1}^{3} H ⟶_{2}^{4} He .$

20.5 Uses of Radioisotopes

55.

How can a radioactive nuclide be used to show that the equilibrium:
$AgCl (s) ⇌ {Ag}^{+} (a q) + {Cl}^{−} (a q)$
is a dynamic equilibrium?

56.

Technetium-99m has a half-life of 6.01 hours. If a patient injected with technetium-99m is safe to leave the hospital once 75% of the dose has decayed, when is the patient allowed to leave?

57.

Iodine that enters the body is stored in the thyroid gland from which it is released to control growth and metabolism. The thyroid can be imaged if iodine-131 is injected into the body. In larger doses, I-133 is also used as a means of treating cancer of the thyroid. I-131 has a half-life of 8.70 days and decays by β⁻ emission.

(a) Write an equation for the decay.

(b) How long will it take for 95.0% of a dose of I-131 to decay?

20.6 Biological Effects of Radiation

58.

If a hospital were storing radioisotopes, what is the minimum containment needed to protect against:

(a) cobalt-60 (a strong γ emitter used for irradiation)

(b) molybdenum-99 (a beta emitter used to produce technetium-99 for imaging)

59.

Based on what is known about Radon-222’s primary decay method, why is inhalation so dangerous?

60.

Given specimens uranium-232 (t_1/2 = 68.9 y) and uranium-233 (t_1/2 = 159,200 y) of equal mass, which one would have greater activity and why?

61.

A scientist is studying a 2.234 g sample of thorium-229 (t_1/2 = 7340 y) in a laboratory.

(a) What is its activity in Bq?

(b) What is its activity in Ci?

62.

Given specimens neon-24 (t_1/2 = 3.38 min) and bismuth-211 (t_1/2 = 2.14 min) of equal mass, which one would have greater activity and why?

License

Icon for the Creative Commons Attribution 4.0 International License

Key Terms

Key Equations

Summaries

20.1 Nuclear Structure and Stability

20.2 Nuclear Equations

20.3 Radioactive Decay

20.4 Transmutation and Nuclear Energy

20.5 Uses of Radioisotopes

20.6Biological Effects of Radiation

Exercises

20.1 Nuclear Structure and Stability

20.2 Nuclear Equations

20.3 Radioactive Decay

20.4 Transmutation and Nuclear Energy

20.5 Uses of Radioisotopes

20.6 Biological Effects of Radiation

License

Share This Book