Ch 9 Nuclear Radiation

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Ch 9 Nuclear Radiation

  1. 1. 1 Ch 9 - Nuclear RadiationCh 9 - Nuclear Radiation 1. Nuclear Emissions 2. Nuclear Equations 3. Producing Radioactive Isotopes 4. Half-Life 5. Nuclear Fission and Fusion 6. Uses & Effects
  2. 2. 2 Review Remember • Protons: + charge • Neutrons: neutral • Electrons: - charge B11 5 atomic symbol atomic number number of protons mass number number of protons and neutrons Nuclear SymbolsNuclear Symbols – notice mass number is on top
  3. 3. 3 1. Nuclear Emissions • Radiation comes from the nucleus of an atom. • Unstable nucleus emits a particle or energy α alpha β beta γ gamma • non-radioactive particle = neutron n1 0
  4. 4. 4 Alpha Particle Same as a helium nucleus (He) 4 2 He or α Two protons Two neutrons
  5. 5. 5 Beta Particle β An electron emitted from the nucleus 0 e or β −1 A neutron in the nucleus breaks down 1 1 0 n H + e 0 1 -1
  6. 6. 6 Gamma γ Radiation • Pure radiation • Like an X-ray but comes from the nucleus
  7. 7. 7 Radiation Protection • Shielding alpha – paper, clothing beta – lab coat, gloves gamma- lead, thick concrete • Limit time exposed • Keep distance from source
  8. 8. 8 Radiation Protection
  9. 9. 9 2. Nuclear Equations2. Nuclear Equations In the reactants and products Atomic numbers must balance and Mass numbers must balance
  10. 10. 10 Alpha decay
  11. 11. 11 Beta decay 234 Th → 234 Pa + 0 e 90 91 −1 beta particle
  12. 12. 12 Gamma radiation No change in atomic or mass number 11 B 11 B + 0 γ 5 5 0 boron atom in a high-energy state
  13. 13. 13 Learning CheckLearning Check • To predict the product, simply remember that the mass number and atomic number are conserved • What is the identity of X? e0 1- 239 92 XU +→
  14. 14. 14 Learning CheckLearning Check Write the nuclear equation for the beta emitter Co-60.
  15. 15. 15 SolutionsSolutions 60 Co 60 Ni + 0 e 27 28 -1 93 239 Npe0 1- 239 92 XU +→
  16. 16. 16 3. Producing Radioactive Isotopes3. Producing Radioactive Isotopes Bombardment of atoms produces radioisotopes = 60 = 60 59 Co + 1 n 56 Mn + 4 He 27 0 25 2 = 27 = 27 cobalt neutron manganese alpha atom radioisotope particle
  17. 17. 17 Learning Check What radioactive isotope is produced in the following bombardment of boron? 10 B + 4 He ? + 1 n 5 2 0
  18. 18. 18 Solution What radioactive isotope is produced in the following bombardment of boron? 10 B + 4 He 13 N + 1 n 5 2 7 0 nitrogen radioisotope
  19. 19. 19 4. Half-Life of a Radioisotope4. Half-Life of a Radioisotope The time for the radiation level to fall (decay) to one-half its initial value
  20. 20. 20 Examples of Half-Life Isotope Half life C-15 2.4 sec Ra-224 3.6 days Ra-223 12 days I-125 60 days C-14 5700 years U-235 710 000 000 years
  21. 21. 21 Learning Check The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 26 hours?
  22. 22. 22 Solution t1/2 = 13 hrs 26 hours = 2 x t1/2 Amount initial = 64mg Amount remaining = 64 mg x ½ x ½ = 16 mg
  23. 23. 23 5. Fission VS Fusion5. Fission VS Fusion Fission large nuclei break up 235 U + 1 n 139 Ba + 94 Kr + 3 1 n + 92 0 56 36 0 Energy
  24. 24. 24 Fission of Uranium-235 • Chain reaction – the reaction sustains itself by producing more neutrons
  25. 25. 25 Nuclear FusionNuclear Fusion Fusion small nuclei combine 2 H + 3 H 4 He + 1 n + 1 1 2 0 Occurs in the sun and other stars Energy • Excessive heat can not be contained • Attempts at “cold” fusion have FAILED. • “Hot” fusion is difficult to contain
  26. 26. 26 Learning CheckLearning Check Indicate if each of the following are (1) Fission (2) fusion A. Nucleus splits B. Large amounts of energy released C. Small nuclei form larger nuclei D. Hydrogen nuclei react Energy
  27. 27. 27 SolutionSolution Indicate if each of the following are (1) Fission (2) fusion A. 1 Nucleus splits B. 1 + 2 Large amounts of energy released C. 2 Small nuclei form larger nuclei D. 2 Hydrogen nuclei react
  28. 28. 28 6. Uses & Effects6. Uses & Effects • Radiation - treatment of cancer • Nuclear medicine - use of radioisotopes in diagnosis – Tracers – small amounts of radioactive substances used as probes to study internal organs – Nuclear imaging – medical techniques involving tracers • Food Irradiation – Food - irradiated with g rays from 60Co or 137Cs. – Irradiated milk - shelf life of 3 mo. w/o cooling. – USDA - approved irradiation of meats and eggs
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  30. 30. 30 Exposure Sources

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