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Chapter 4

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Chapter 4

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  1. Chapter 4 Chad Stessman

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

  3. 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

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

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

  6. 14C incorporates into living creatures through the carbon cycle.

  7. 14C incorporates into living creatures through the carbon cycle • When plant or animal dies, it is no longer incorporating 14C

  8. 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

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

  10. Other isotopes used in dating • Potassium-40 1.3x109 years • Rhenium-187 4.3x1010 years • Uranium-238 4.5x109 years

  11. Artificial Transmutation • Middle ages alchemists tried to accomplish transmutation • Nuclear reactions can change atoms

  12. Uses of Radioisotopes • Around 3000 radioactive isotopes can be produced from stable isotopes.

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

  14. Nuclear Medicine • Radiation Therapy • Diagnostic Uses

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

  16. 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

  17. Used in gamma imaging of heart.