Chad Stessman

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Chapter 4

• Chad Stessman

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Half-life

• Radioactivity is a random process
• Half life is time it take half of the atoms of a
  sample to decay

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Half-lives

• Tritium-3H- half life of 12.3 years
• 238U has a half life of 3.8 billion years
• Amount remaining after a certain number of
  half-lives is 1/2n. Where n number of half lives

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Radioisotope dating

• Radioactive decay can be used to determine the
  age of a sample.

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Carbon-14 dating

• 14C is an isotope of carbon.
• Formed by bombardment of nitrogen in the
  atmosphere with cosmic rays, neutrons

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• 14C incorporates into living creatures through
  the carbon cycle.

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• 14C incorporates into living creatures through
  the carbon cycle
• When plant or animal dies, it is no longer
  incorporating 14C

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• 14C half life is 5730 years
• After about 10 half-lives or 50,000 years too
  little 14C to be effective.
• 14C formation not always constant, need to find
  references

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Tritium Dating

• 3H has a half-life of 12.3 years
• Used to determine age of brandy and wine samples
  10-100 years old

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Other isotopes used in dating

• Potassium-40 1.3x109 years
• Rhenium-187 4.3x1010 years
• Uranium-238 4.5x109 years

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Artificial Transmutation

• Middle ages alchemists tried to accomplish
  transmutation
• Nuclear reactions can change atoms

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Uses of Radioisotopes

• Around 3000 radioactive isotopes can be produced
  from stable isotopes.

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Tracers

• Used in physical, chemical or biological systems.
• Used to look for leaks, follow reactions, get
  images of biological processes.

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Nuclear Medicine

• Radiation Therapy
• Diagnostic Uses

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Radiation Therapy

• Use radiation to destroy rapidly growing cancer
  cells.
• Aim radiation at cancer cells

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Diagnostic Uses of Radiation

• Radioisotopes are use to image or diagnose
  problems with the body functioning.
• Technium-99m-gives up a gamma ray to become more
  stable
• 99mTc 99Tc gamma

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• Used in gamma imaging of heart.