Nuclear chemistry

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  • 50 after 1 year. 25 after 2 years.
  • Nuclear chemistry

    1. 1. Nuclear Chemistry P Squires Basic Chemistry 2005-2006
    2. 2. Isotopes ……have the same number ofprotons and electrons butdifferent numbers ofneutrons.
    3. 3. Isotopes ……have different mass numbers but the same atomic number.
    4. 4. Symbols for Isotopes Mass number Symbol U 235 92 of ElementAtomicnumber
    5. 5. Symbols for Isotopes Mass numberA is the A Symbol Esymbol formass ofnumber Z Element Z is the symbol for Atomic atomic number number
    6. 6. IsotopesConsider an atom of aluminum with 13 protons and 15 neutrons. What is Z and A? A = #p + #n + 13 + 15 = 28
    7. 7. How are isotopes of the same element alike and different?Alike: Different:1. Number of 1. Number of protons and neutrons electrons2. Atomic number 2. Mass Number3. Chemical 3. Atomic weight of properties the isotopes
    8. 8. Isotopes See IllustratedIsotope example
    9. 9. Finding the number of Protons, Neutrons, and ElectronsThe atomic number is the number of protons in the nucleus.The number of electrons in a neutral atom equals the number of protons.
    10. 10. Finding the number of Protons, Neutrons, and Electrons# of neutrons = A - Z
    11. 11. Finding the number of Protons, Neutrons, and ElectronsZ = 92 U-235protons = 92electrons = 92 A = 235 protons + neutrons = 235
    12. 12. Finding the number of Protons, Neutrons, and ElectronsQ. Find the number of neutrons in the Ba-137 isotope.
    13. 13. Finding the number of Protons, Neutrons, and ElectronsElement Symbol Z A #p #n #e Zinc 66 In 68 85 38 82 210 Rn 136 35 47
    14. 14. Finding the number of Protons, Neutrons, and ElectronsElement Symbol Z A #p #n #e Zinc Zn 30 66 30 36 30 In 68 85 38 82 210 Rn 136 35 47
    15. 15. Finding the number of Protons, Neutrons, and ElectronsElement Symbol Z A #p #n #e Zinc Zn 30 66 30 36 30Indium In 49 117 49 68 49 85 38 82 210 Rn 136 35 47
    16. 16. Finding the number of Protons, Neutrons, and ElectronsElement Symbol Z A #p #n #e Zinc Zn 30 66 30 36 30 Indium In 49 117 49 68 49Strontium Sr 38 85 38 47 38 82 210 Rn 136 35 47
    17. 17. Finding the number of Protons, Neutrons, and ElectronsElement Symbol Z A #p #n #e Zinc Zn 30 66 30 36 30 Indium 49 117 49 68 49Strontium Sr 38 85 38 47 38 Lead Pb 82 210 82 128 82 Rn 136
    18. 18. Finding the number of Protons, Neutrons, and ElectronsElement Symbol Z A #p #n #e Zinc Zn 30 66 30 36 30 Indium In 49 117 49 68 49Strontium Sr 38 85 38 47 38 Lead Pb 82 210 82 128 82 Radon Rn 86 222 86 136 86 35 47
    19. 19. Finding the number of Protons, Neutrons, and ElectronsElement Symbol Z A #p #n #e Zinc Zn 30 66 30 36 30 Indium In 49 117 49 68 49Strontium Sr 38 85 38 47 38 Lead Pb 82 210 82 128 82 Radon Rn 86 222 86 136 86Bromine Br 35 82 35 47 35
    20. 20. Only one element has unique names for its isotopes … 1 1 H = hydrogen 2 1 H = deuterium 3 1 H = tritiumDeuterium and tritium are used innuclear reactors and fusion research.
    21. 21. Some isotopes are radioactive• Radioactive isotopes are called radioisotopes.• Radioisotopes can emit alpha, beta or gamma radiation as they decay.• Radioisotopes are important in a number of research fields.
    22. 22. Protection from radiation1. Shielding2. Distance
    23. 23. Protection from radiation How do you protect yourself from …Alpha 2.5 cm of air, paper, skin aluminum, lead, otherBeta metals, wood, plastic, etc.Gamma up to a foot or two of lead, many feet of concrete
    24. 24. Properties of Alpha Particles• Alpha (α) particles are the nuclei of helium atoms and have the symbol 2He 4
    25. 25. Properties of Beta ParticlesBeta (β) particles are high speed electrons ejected from the nuclei of atoms and have the symbol -1e .0
    26. 26. Properties of Gamma Rays• Gamma (γ) rays are high energy electromagnetic waves, not particles.• Gamma rays have short wavelengths and high energies and travel at the speed of light.
    27. 27. Alpha, Beta, Gamma Electrically charged plates + + + + + + + + What is the effect of electrically charged plates on α, β, γ ? - - - - - - - - -Radioactive Source
    28. 28. Alpha, Beta, Gamma Electrically charged plates + + + + + + + + β γ - - - - - - - - - αRadioactive Source
    29. 29. Alpha, Beta, Gamma Why do the α, β and γ rays take the paths that they do?
    30. 30. Alpha, Beta, Gamma Paper Lead α AluminumRadioactive foilSource
    31. 31. Alpha, Beta, Gamma Paper Lead β α AluminumRadioactive foilSource
    32. 32. Alpha, Beta, Gamma Paper Lead β γ α AluminumRadioactive foilSource
    33. 33. Decayequations
    34. 34. Alpha DecayIn alpha decay, an alpha particle (2He4) is released from the nucleus.
    35. 35. Alpha decay decay product92 U 238  2He + 90Th 4 234 alpha particle
    36. 36. Alpha decayRadon-220 decays by alpha emission.What is the decay product? 86 Rn 220  2He + 4 84 Po ???216
    37. 37. Alpha decayWrite the alpha decay equations for:1. 95Am 241 2He + 93Np 4 2372. 84Po 216  2He + 82Pb 4 2123. 88Ra 226  2He + 86Rn 4 222
    38. 38. Beta DecayBeta decay occurs because of the instability of a neutron.Neutrons are a little more massive than protons; and neutrons are neutral.
    39. 39. Beta decayDecay of a neutron: 0n1  1H1 + -1e0 neutron proton electronThe electron ejected from thenucleus is a beta particle.
    40. 40. Start with a Li atom with Beta decay3 protons and Suddenly a 4 neutrons. neutron decays! Now there A beta particle are 4 protons goes zipping out ofand 3 neutrons. the nucleus.
    41. 41. Beta decay decay product6 C 14  7N 14 + -1e 0 beta particle
    42. 42. Beta decayZn-62 decays by beta emission.What is the decay product? 30 Zn  -1e + 62 0 ??? 31Ga 62
    43. 43. Beta decayWrite the beta decay equations for:1. 82Pb214  -1 e + 83Bi 0 2142. 27Co  62 -1 e + 28Ni 0 623. 47???  Ag 113 -1 e + 48Cd 0 113
    44. 44. Gamma Decay•Gamma rays are neutraland thus no change ismade in the equation. 6 C 14  6C 14 +¥
    45. 45. Half life
    46. 46. What is half life?Half life is the time needed for one half of a radioisotope to decay.
    47. 47. Half Life• Take 100 pennies and throw them on the floor.• Remove those that are heads up.• Count remaining pennies.• Continue until only one penny remains. What can this tell us about Half Life?
    48. 48. What is half life? • Suppose you start with 100.0 grams of a radioisotope that has a half life of exactly 1 year.How much will be left after 1 year?How much will be left after 2 years?
    49. 49. Half life projectQuestions:1. A radioisotope has a half-life of 100 years. How long will it take for the radiation to decrease to 1/16 of its original value? 400 years
    50. 50. Half life projectQuestions:2. A radioisotope has an activity of 560 counts per minute. After 16 hours the count rate has dropped to 35 counts per minute. What is the half life of the radioisotope? 4 hours
    51. 51. Nuclear Fission
    52. 52. Nuclear fissionFission – the splitting of an atom after being struck by a neutron.
    53. 53. Nuclear Fission
    54. 54. Nuclear fission Fission fragment U-235 U-235 NeutronsNeutron Fission fragment U-235
    55. 55. Nuclear fissionTo picture a chain reaction, imagine50 mousetraps in a wire cage. And on each mousetrap are two ping-pong balls.Now imagine dropping one moreping-pong ball into the cage …
    56. 56. Detail ofping-pongballs onmousetraps.http://www.physics.montana.edu/demonstrations/video/modern/demos/mousetrapchainreaction.html
    57. 57. http://www.physics.montana.edu/demonstrations/video/modern/demos/mousetrapchainreaction.html
    58. 58. http://www.physics.montana.edu/demonstrations/video/modern/demos/mousetrapchainreaction.html
    59. 59. Nuclear fission This heat energy can be harnessed to boil water,creating steam, that can turn a generator, creating electricity.
    60. 60. Nuclear Fusion
    61. 61. Nuclear fusion A day without sunshine is a day without fusion.
    62. 62. Nuclear Fusion
    63. 63. How do we detect radiation?
    64. 64. Geiger-Mueller Tube Counter 2435 Wire (+ side of circuit) Metal shield (- side) Low pressure Ar gasMica window (fragile)
    65. 65. GM Tube Rays leave the source Some hit the GM tube Most do nothing One ray may cause a discharge…Source and the detector clicks
    66. 66. GM TubeFilled with low pressure argon gas About 1% efficiencyAbout 1 in 100 rays causes an electric spark between the case and the wire Each spark registers as a count or click on the counter
    67. 67. Nuclear Fuel Cycle
    68. 68. Nuclear Fuel Cycle• The Nuclear Fuel Cycle consists of sequence of steps in which uranium ore is mined, milled, enriched, and fabricated into nuclear fuel and then irradiated in a reactor for several years.• The entire fuel cycle lifetime from mining to discharge is about 8 years.
    69. 69. Where is Nuclear Waste Kept?• After irradiation the fuel is cooled in the spent fuel pit for several years and then moved to dry cask storage on the reactor site.
    70. 70. Spent Nuclear Fuel Pool • Keep spent fuel rods under at least 20 feet of water to provide adequate shielding from the radiation for anyone near the pool • Spent Fuel Pools were designed as TEMPORARY storage for fuel while short lived isotopes decay (<1 yr)
    71. 71. NUCLEAR REACTOR CORE
    72. 72. US Nuclear Power Plants
    73. 73. Radioactive Decay
    74. 74. The uranium decayseries Uranium-238 decays through many steps to make stable lead-206
    75. 75. Nuclide Half-Life Radiation * U-238 4.468 · 109 years alpha Th-234 24.1 days betaPa-234m 1.17 minutes betaU-234 244,500 years alphaTh-230 77,000 years alphaRa-226 1,600 years alphaRn-222 3.8235 days alphaPo-218 3.05 minutes alphaPb-214 26.8 minutes betaBi-214 19.9 minutes betaPo-214 63.7 microseconds alphaPb-210 22.26 years betaBi-210 5.013 days beta
    76. 76. The uranium decayseries Radon is the only gas present in the decay process.
    77. 77. Start Symbol and U-238 Atomic numberAlpha r e b m n ss a MBeta The uranium decay u End series in NC EOC Pb-206 reference pages
    78. 78. Hazards from radon• Radon gas works its way up through the ground and into your basements and crawl spaces.• You breathe radon into your lungs.
    79. 79. Hazards from radon• When a radon atom decays it releases an alpha particle … …which travels only a short distance before it is absorbed by your lungs, and transfers its energy.
    80. 80. Hazards from radonThis ionizing radiation in yourlungs can cause lung cancer. Smoking cigarettes and breathing radon really increases your chances of getting lung cancer.
    81. 81. Half Life Project
    82. 82. Half life project1. Pick a mass between 10g and 50g.2. Decide on a half life – any time.3. Scale your graph – mass on y-axis and at least six (6) half-lives on the x- axis.4. Plot the masses after intervals of one half-life.
    83. 83. Half life project5. What shape is the graph?6. When will the mass of the radioisotope fall to zero?7. When is the radioactivity no longer a problem?8. What mathematical function describes radioactive decay?

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