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What is radiation?

Bell Ringer. What is radiation?. Video. Ionizing Radiation. Radiation Therapy. Nuclear Reactor. Nuclear Chemistry. Applications. Stability. “Zone of stability”. fission. medical. Radioactive Decay. fusion. Half- Life. Balancing Nuclear Reactions. beta. MASS DEFECT. gamma.

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What is radiation?

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  1. Bell Ringer What is radiation? Video

  2. Ionizing Radiation Radiation Therapy Nuclear Reactor

  3. Nuclear Chemistry Applications Stability “Zone of stability” fission medical Radioactive Decay fusion Half- Life Balancing Nuclear Reactions beta MASS DEFECT gamma alpha Binding Energy

  4. Nuclear Chemistry

  5. Radioactivity Marie Curie  Mini-Biography One of the pieces of evidence for the fact that atoms are made of smaller particles came from her work (1876-1934). She discoveredradioactivity, the spontaneous disintegration of some elements into smaller pieces.

  6. Nuclear Reactions vs. Normal Chemical Changes • Nuclear reactions involve the nucleus • The nucleus opens, and protons and neutrons are rearranged • The opening of the nucleus releases a tremendous amount of energy that holds the nucleus together – called binding energy • “Normal” Chemical Reactions involve electrons, not protons and neutrons

  7. Energy Mass Speed of light Mass Defect • Some of the mass can be converted into energy • Shown by a very famous equation! E=mc2

  8. Types of Radiation See Reference Table O • Alpha (ά) – a positively charged helium isotope - we usually ignore the charge because it involves electrons, not protons and neutrons • Beta (β) – an electron • Gamma (γ) – pure energy; called a ray rather than a particle

  9. Other Nuclear Particles See Reference Table O Neutron Positron – a positive electron Proton – usually referred to as hydrogen-1

  10. Penetrating Ability

  11. Balancing Nuclear Reactions • In the reactants and products: • Atomic numbers must balance • and • Mass numbers must balance • Use a particle or isotope to fill in the missing protons and neutrons

  12. Nuclear Reactions Alpha emission

  13. Nuclear Reactions Beta emission

  14. Bell Ringer Write the nuclear equation for the beta emitter Te-99?

  15. Examples - Determine the missing nuclear particle Beta decay Beta decay Alpha decay Beta decay Now go back and label the reactions as alpha or beta decay Use Table N to determine the products of the following Beta decay 36 Alpha decay 90

  16. Separating Radioactive Emissions You can determine which particles are given off in some cases by observing how the particle reacts in an electric field. (-) charged + + + + + Electron (beta particle) (0) charged Neutrons, gamma radiation - - - - - Radiation source (+) charged Proton, positron, alpha particle A positively charged particle will bend toward the negative plate A negatively charged particle will bend toward the positive plate A neutral particle will not bend in either direction

  17. Half-Life • HALF-LIFE is the time that it takes for 1/2 a sample to decompose. • The rate of a nuclear transformation depends only on the “reactant” concentration.

  18. Half-Life Decay of 20.0 mg of 15O. What remains after 3 half-lives? After 5 half-lives?

  19. Kinetics of Radioactive Decay For each duration (half-life), one half of the substance decomposes. For example: Ra-234 has a half-life of 3.6 daysIf you start with 50 grams of Ra-234 After 3.6 days > 25 grams After 7.2 days > 12.5 grams After 10.8 days > 6.25 grams

  20. Half-Life Problems What fraction of a sample of Sr-90 will remain after 175 years? 1. Get the half life from Table N 29.1 years 2. Determine how many half-lives elapsed in the time period. 3. Calculate the fraction remaining 1 2 3 4 5 6 1/64 1 ½ ½ ½ ½ ½ ½ =

  21. Half-Life Problems If a sample of Sr-90 has an original mass of 52.0g, what mass will remain after 175 years? 1 2 3 4 5 6 52.0 26.0 13.0 6.50 3.25 1.63 .815 g OR 52.0 g x 1/64 = .815 g

  22. + - Bell Ringer The above diagram represents radiation passing through an electric field. Label arrows 1, 2 and 3 with respect to what type of emanation they represent. 1 2 3

  23. Half Life Lab

  24. Bell Ringer If Brandon has 0.2 grams of Iodine-131 in his body after 40.35 days, how much I-131 did he have injected in his body?

  25. Types of Transmutations 12 6 14 6 C C A. Natural Radioactivity (Transmutation) Many nuclei of atoms are very stable, others are unstable and will decay Based on the ratio of protons to neutrons Further from a 1:1 ratio, more likely to decay 6 protons, 6 neutrons stable 6 protons, 8 neutrons unstable Larger atoms are generally more unstable All are radioactive No stable isotopes past Pb

  26. Band of Stability and Radioactive Decay

  27. Types of Transmutations B. Artificial Radioactivity (Transmutation) Some atoms are forced to decay into other atoms Process involves bombarding a stable nucleus with accelerated particles Speed up subatomic particles and hit them against nuclei You can identify an artificial transmutation because it will have two reactants!

  28. Identify the type of transmutation(artificial or natural)

  29. Bell Ringer It could take up to 60 hours for a radioisotope to be delivered to a hospital. What fraction of an original sample of Na-24 remains unchanged after 60 hours? [Half life = 15 hours]

  30. Quiz - Isotopes Explain the function for each of the following: • C-14 • I-131 • Co-60 • Tc-99 • Gamma radiation

  31. Nuclear Fission FISSION = DIVISION Fission is the splitting of atoms These are usually very large, so that they are not as stable

  32. Nuclear Fission Nuclear Chain reactions

  33. Representation of a fission process.

  34. Nuclear Fission & POWER • Currently about 103 nuclear power plants in the U.S. and about 435 worldwide. • 17% of the world’s energy comes from nuclear.

  35. Figure 19.6: Diagram of a nuclear power plant.

  36. ENERGY Nuclear Fusion Fusion small nuclei combine Occurs in the sun and other stars

  37. Nuclear Bomb explosion at Bikini Island 1961

  38. Nuclear Fusion Fusion • Excessive heat can not be contained • Attempts at “cold” fusion have FAILED. • “Hot” fusion is difficult to contain • Fusion bombs video

  39. Effects of Radiation

  40. Bell Ringer If you had 800g of Francium-220 137.5 seconds ago. How much would you currently have?

  41. Benefits of RadioisotopesTracers • aka  Radioactive label • Tracers – makes chemicals radioactive, so we can see where they go

  42. PET Scan Benefits of RadioisotopesMedicine Radioisotopes with very short half lives are used to diagnose AND treat illnesses • Tc-99  marks brain tumors • I-131  detect/treat thyroid illness • Ra-226  treats cancer • Co-60  treats cancer

  43. Benefits of RadioisotopesFood irradiation • - exposes fresh foods to radiation to kill microorganisms • Food can be irradiated with g rays from 60Co or 137Cs. • Irradiated milk has a shelf life of 3 mo. without refrigeration. • USDA has approved irradiation of meats and eggs.

  44. Benefits of RadioisotopesRadioactive Dating • Geologic  U-238 decays into Pb-206 • Biological  ratio of C-12 to C-14 to date organic items

  45. Benefits of Radioisotopes • Nuclear Power • Relatively inexpensive • No greenhouse gases • Industrial Measurement • Measure the volume • Thickness of materials

  46. Risks of RadioisotopesBiological Damage Can damage or destroy cells, cause burns Damage reproductive organs

  47. Risks of RadioisotopesStorage of wastes Who wants it in their backyard for the next 1000000 years? • Yucca Mountain 100 miles NW of Las Vegas Already spent 15 billion and now going to be closed!!!

  48. Risks of RadioisotopesNuclear Accidents • Chernobyl – overheating caused by improper withdrawal of control rods • Caused an explosion – released radioactive materials into the air • As of 2004 54 people killed as a result

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