The Nucleus, Radioactivity, and Nuclear Medicine

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Chapter 10

• The Nucleus, Radioactivity, and Nuclear Medicine

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10.1 Natural Radioactivity

• Radioactivity
• Radiation
• Nuclear symbols

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10.1 Natural Radioactivity
mass number
atomic symbol
atomic number

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• Remember for section 2.2, this defines an isotope
  of boron.
• This is not the only isotope (nuclide) of boron.
• boron-10 also exists
• How many protons and neutrons does boron-10 have?

10.1 Natural Radioactivity
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• Some isotopes are stable
• The unstable isotopes are the ones that produce
  radioactivity.
• To write nuclear equations (section 10.2) we need
  to be able to write the symbols for the isotopes
  and the following
• alpha particle
• beta particles
• gamma rays

10.1 Natural Radioactivity
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Alpha Particles
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• Alpha particle (a)
• Symbolized in the following ways

10.1 Natural Radioactivity
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Bata Particles
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• Bata particles (b)

10.1 Natural Radioactivity
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Gamma Rays
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• Gamma Rays (g)
• Symbol is simply

10.1 Natural Radioactivity
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Properties of Alpha, Beta, and Gamma Radiation
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• Ionizing radiation
• The penetrating power of the radiation determines
  the ionizing damage that can be caused.

10.1 Natural Radioactivity
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10.2 Writing a Balanced Nuclear Equation
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• Nuclear equation -
• In a nuclear equation, you do not balance the
  elements, instead...

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10.2 Writing Balanced Nuclear Equations
Alpha Decay
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Beta Decay
10.2 Writing Balanced Nuclear Equations
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Gamma Production

• Gamma radiation occurs to increase the stability
  of an isotope.
• The atomic mass and number do not change.

10.2 Writing Balanced Nuclear Equations

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Predicting Products of Nuclear Decay

• To predict the product, simply remember that the
  mass number and atomic number is conserved.

10.2 Writing Balanced Nuclear Equations

• What is the identity of X?

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10.3 Properties of Radioisotopes

• Nuclear Structure and Stability
• Binding Energy -

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10.3 Properties of Radioisotopes

• Important factors for stable isotopes.
• Ratio of neutrons to protons.
• Nuclei with large number of protons (84 or more)
  tend to be unstable.
• The magic numbers of 2, 8, 20, 50, 82, or 126
  help determine stability. These numbers of
  protons or neutrons are stable.
• Even numbers of protons or neutrons are generally
  more stable than those with odd numbers.
• All isotopes (except 1H) with more protons than
  neutrons are unstable.

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Half-Life
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• Half-life (t1/2) -
• Each radioactive isotope has its own half-life

10.3 Properties of Radioisotopes
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10.3 Properties of Radioisotopes
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Half-Life Calculation
A patient receives 10.0 ng of a radioisotope with
a half-life of 12 hours. How much will remain in
the body after 2.0 days, assuming that
radioactive decay is the only path for removal of
the isotope form the body.
10.3 Properties of Radioisotopes
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10.4 Nuclear Power
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• Energy Production
• Equation by Albert Einstein shows the connection
  between energy (E) and the mass (m)
• c is the speed of light

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10.4 Nuclear Power
Nuclear Fission

• Fission

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10.4 Nuclear Power

• Chain reaction -

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• A nuclear power plant uses a fissionable material
  as fuel.

10.4 Nuclear Power
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Nuclear Fusion

• Fusion (to join together) -
• Best example is the sun.
• An Example

10.4 Nuclear Power

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Breeder Reactors

• Breeder reactor -
• Uranium-238 (non fissionable) is converted to
  plutonium-239 (fissionable).
• Plutonium-239 undergoes fission to produce
  energy.

10.4 Nuclear Power
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10.5 Radiocarbon Dating
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• Radiocarbon dating -
• Ratio of carbon-14 and carbon-12
• Basis for dating
• Carbon-14 (a radioactive isotope) is constantly
  being produced by neutrons from the sun.

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10.5 Radiocarbon Dating

• Living systems are continually taking in carbon.
• Once the living system dies, it quits taking in
  the carbon-14.

• The half-life of carbon-14 is 5730 years.
• This information is used to calculate the age.

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10.6 Medical Applications of Radioactivity
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• Modern medical care uses the following
• Nuclear medicine

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10.6 Medical Applications

• Cancer Therapy Using Radiation
• Based on the fact that high-energy gamma rays
  cause damage to biological molecules.
• Tumor cells are more susceptible then normal
  cells.
• Example cobalt-60
• Gamma radiation can cure cancer but can also
  cause cancer.

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• Nuclear Medicine
• The use of isotopes in diagnosis.
• Tracers -
• Nuclear imaging -
• Example
• Iodine concentrates in the thyroid gland.
• Using radioactive 131I and 125I will allow the
  study of how the thyroid gland is taking in
  iodine.

10.6 Medical Applications
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• Isotopes with short half-lives are preferred for
  tracer studies. Why?
• Examples of imaging procedures
• Bone disease and injury using technetium-99m
• Cardiovascular disease using thallium-201
• Pulmonary disease using xenon-133

10.6 Medical Applications
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Making Isotopes for Medical Applications
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• Artificial radioactivity -
• Made in two ways
• In particle accelerators -

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10.6 Medical Applications
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Examples of artificial radioactivity

• Tracer in the liver

10.6 Medical Applications

• Used in the diagnosis of Hodgkins disease.

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• Some isotopes used in nuclear medicine have such
  a short half-life that they need to be generated
  on site.
• 99mTc has a half-life of only 6 hours.

10.6 Medical Applications
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10.7 Biological Effects of Radiation
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• Radiation Exposure and Safety
• The Magnitude of the Half-Life
• Isotopes with short half-lives have one major
  disadvantage and one major advantage.

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10.7 Biological Effects

• Shielding
• Distance from the Radioactive Source

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• Time of Exposure
• Types of Radiation Emitted
• Waste Disposal

10.7 Biological Effects
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10.8 Detection and Measurement of Radiation
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• Nuclear Imaging

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10.8 Detection and Measurement of Radiation

• Computer Imaging
• Computers and television are coupled

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The Geiger Counter

• Detects ionizing radiation

10.8 Detection and Measurement of Radiation

• Has largely been replaced by more sophisticated
  devises.

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Film Badges

• A piece of photographic film that is sensitive to
  energies corresponding to radioactive emissions.
• The darker the film, when developed, the longer
  the worker has been exposed.

10.8 Detection and Measurement of Radiation
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10.9 Units of Radiation Measurement
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• The Curie
• The amount of radioactive material that produces
  3.7 x 1010 atomic disintegrations per second.
• Independent of the nature of the radiation

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10.9 Units of Radiation Measurement

• The Roentgen
• The amount of radiation needed to produce 2 x 109
  ion pairs when passing through one cm3 of air at
  0oC.
• Used for very high energy ionizing radiation only.

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• Rad
• Radiation absorbed dosage.
• The dosage of radiation able to transfer 2.4 x
  10-3 cal of energy to one kg of matter.
• This takes into account the nature of the
  absorbing material.

10.9 Units of Radiation Measurement
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• The Rem
• Roentgen Equivalent for Man
• Obtained by multiplication of the rad by a factor
  called the relative biological effect (RBE)
• RBE 10 for alpha particles
• RBE 1 for beta particles
• Lethal dose (LD50) - the acute dosage of
  radiation that would be fatal for 50 of the
  exposed population.
• LD50 500 rems.

10.9 Units of Radiation Measurement
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The End Chapter 10