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Ch18 z7e nuclear

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  • Z5e 1022
  • Hrw 705-707; z5e 1024-1025
  • Hrw 706; z5e 1024
  • Hrw 706; z5e 1024-1025
  • Hrw 707; z5e 1024-1025
  • Hrw 707; z5e 1027
  • Hrw 710 z53 1027
  • Z5e 1028
  • Hrw 708; z5e 1028
  • Hrw 708; z5e 1030
  • Hrw 709; z5e 1028
  • Hrw 709; z5e 1028
  • Z5e text #21
  • AP 1989 MC #68
  • Z5e text #21
  • Hrw 714; z53 1033-1044
  • Hrw 715; z5e 1034
  • Hrw none; z5e 1032
  • Z5e 1035 SE 21.5
  • Z5e 1035 SE 21.5
  • Z5e 1035 SE 21.6
  • Hrw 715; z5e 1037
  • Hrw 715; z5e 1037
  • Hrw 715; z5e 1038
  • Hrw 701; Z5e 1038
  • Hrw 701-702; Z5e 1038-40
  • Hrw 702; z5e 1038-40
  • Z5e 1042 Fig. 21.10
  • Hrw 717; z5e 1042-1044
  • Hrw 718; no 1044
  • Hrw 718; z5e 1044
  • Hrw 1044; no z5e
  • Hrw 717; z5e 1042-1044
  • Hrw 718
  • Hrw 719; z5e 1047-1048
  • None (z5e 1044-1047)
  • Hrw none, z5e 1044-1047
  • Hrw 717-719; z5e 1041-1042
  • Hrw 716; z5e 1044
  • Z5e 1048
  • Hrw 713; z5e 1048
  • Hrw 715; z5e 1038

Transcript

  • 1. CHAPTER 18 Nuclear Chemistry 18.I Nuclear Stability & Radioactive Decay pp I
  • 2. Black dots are stable nuclides. As A (atomic mass) increases, nº/p + ratio increases.
  • 3. Subatomic Particles
    • Protons - plus charge
            • In the nucleus
    • Neutrons - neutral
    • Electrons - negative charge
    • Outside the nucleus
  • 4. Radiation
    • Radiation comes from the nucleus of an atom.
    • Unstable nucleus emits a particle or energy  alpha
    •  beta
    •  gamma
  • 5. Types of Radiation
    • Alpha particle (  )
      • helium nucleus
    paper 2+
    • Beta particle (  -)
      • electron
    1- lead
    • Positron (  +)
      • positron
    1+
    • Gamma (  )
      • high-energy photon
    0 concrete
  • 6. Radiation Protection
    • Shielding
    • alpha – paper, clothing
    • beta – lab coat, gloves
    • gamma- lead, thick concrete
    • Limit time exposed
    • Keep distance from source
  • 7. Radiation Protection
  • 8. Nuclear Decay
    • Alpha Emission
    Atomic & Mass Numbers must balance!! parent nuclide daughter nuclide alpha particle
  • 9. Nuclear Decay
    • Beta Emission
    • Positron Emission
    electron positron
  • 10. Nuclear Decay
    • Electron Capture (of inner orbital electrons)
    • Gamma Emission
      • Usually follows other types of decay.
    • Transmutation
      • One element becomes another.
    electron
  • 11.  
  • 12. Gamma radiation
    • No change in atomic or mass number
    • 11 B 11 B + 0 
    • 5 5 0
    • boron atom in a
    • high-energy state
  • 13.  
  • 14. Table 18.2 Types of Nuclear Processes p. 845
  • 15. Learning Check
    • Write the nuclear equation for the beta emitter Cobalt-60. . .
    • 60 Co 60 Ni + 0 e 27 28 -1
  • 16. Producing Radioactive Isotopes
    • Bombardment of atoms produces radioisotopes
    • = 60 = 60
    • 59 Co + 1 n 56 Mn + 4 H e
    • 27 0 25 2
    • = 27 = 27
    • cobalt neutron manganese alpha
    • atom radioisotope particle
  • 17. Learning Check NR2
    • What radioactive isotope is produced in the following bombardment of boron?
    • 10 B + 4 He ? + 1 n
    • 5 2 0
  • 18. Solution NR2
    • 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. Nuclear Decay pp
    • Why nuclides decay…
      • need stable ratio of neutrons to protons
    DECAY SERIES TRANSPARENCY
  • 20. The decay series.
  • 21. 18.2 Kinetics of Radioactive Decay
    • Rate of decay is a 1st order process, which is . . .
    • ln(N/N 0 ) = -kt (memorize -- not on AP sheet)
    • N 0 = original number of nuclides at t = 0 N = nuclides remaining at time t
    • Half-life (t 1/2 ) = time for nuclides to reach half their original value.
    • t 1/2 = 0.693/k
  • 22. Half-life
    • Half-life (t 1/2 )
      • Time required for half the atoms of a radioactive nuclide to decay.
      • Shorter half-life = less stable.
  • 23.  
  • 24. 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
  • 25. Learning Check NR3
    • The half life of Iodine-123 is 13 hr. How much of a 64 mg sample of Iodine-123 is left after 26 hours?
  • 26. Solution NR3
    • t 1/2 = 13 hrs
    • 26 hours = 2 x t 1/2
    • Amount initial = 64mg
    • Amount remaining = 64 mg x 1/2 x 1/2
    • = 16 mg
  • 27. Half-life m f : final mass m i : initial mass n : # of half-lives
  • 28. Half-life pp
    • Fluorine-21 has a half-life of 5.0 seconds. If you start with 25 g of fluorine-21, how many grams would remain after 60.0 s?
    GIVEN: T 1/2 = 5.0 s m i = 25 g m f = ? total time = 60.0 s n = 60.0s ÷ 5.0s =12 WORK : m f = m i (1/2) n m f = (25 g)(0.5) 12 m f = 0.0061 g
  • 29. Kinetics of Nuclear Decay Problems pp
    • The rate constant for 99 43 Tc = 1.16 x 10 -1 /h What is its half life? . . .
    • t 1/2 = 0.693/k = 0.693/(1.16 x 10 -1 /h) = 5.98 h
    • It will take 5.98 hours for a given sample of technetium-99 to decrease to half the original number of nuclides.
  • 30. Kinetics of Nuclear Decay Problems pp
    • How long for 87.5% of a sample of cobalt-60 to decay if t 1/2 = 5.26 years? Steps. . .
    • What % is left? . . .
    • 12.5%
    • How many half-lives to get to this percent?
    • 3. So, your answer to the problem is . . .
    • 3 x 5.26 = 15.8 years.
  • 31. Actual AP question: 1989 MC #68 pp
    • If k = 0.023 min -1 how much of X was originally present if have 40. g after 60 min.?
    • Your answer is . . .
    • 160. g . Solution . . .
    • t 1/2 = 0.693/k = 0.693/0.023 min -1 = 30 min. 60 minutes is 2 half-lives so going backwards 40. g to 80. g to 160. g.
  • 32. 18.3 Nuclear Transformations
    • Transmutation - change of one element into another.
    • Particle and linear accelerators are used to synthesize new elements (currently up to element number 119).
    • Difficult to characterize the chemical properties because with some only a few atoms are formed with very short half-lives.
  • 33. A representation of a Geiger-Müller counter.
  • 34. 18.4 Detection & Uses of Radioactivity
    • Half-life measurements of radioactive elements are used to determine the age of an object
    • Decay rate indicates amount of radioactive material
    • EX : 14 C - up to 40,000 years 238 U and 40 K - over 300,000 years
  • 35. Synthetic Elements
    • Transuranium Elements
      • elements with atomic #s above 92
      • synthetically produced in nuclear reactors and accelerators
      • most decay very rapidly
  • 36. Carbon-14 Dating You will have a test question like this! pp
    • An ancient fire in an African cave has a 14 C decay rate of 3.1 cpm (cts per minute). If fresh wood has 13.6 cpm how old is the campfire if t 1/2 = 5730 years? Steps . . .
    • Decay rates are directly proportional to nuclides so their ratio = N/N 0 What is the numerical ratio? Your answer . . .
    • 3.1 cpm/13.6 cpm = 0.23
    • Use the two previous equations to solve (next slide).
  • 37. Carbon-14 Dating You will have a test question like this! pp
    • Ancient fire 14 C decay rate 3.1 cpm, fresh wood 13.6 cpm how old if t 1/2 = 5730 yrs ?
    • 3.1 cpm/13.6 cpm = 0.23 = N/N 0
    • ln(N/N 0 ) = - k t and t 1/2 = 0.693/ k
    • You want to solve for t (vs. t 1/2 ) so use t 1/2 to get k then plug into the 1st equation and solve for t. Your answer is . . .
    • The campfire is 12 000 years old. ln( N/N 0 ) = ln( 0.23 ) = -(0.693/ 5730 ) t
    • Se Ex 18.4A & 18.4B in Study Guide
  • 38. Carbon-14 Dating You will have another test question like this ! pp
    • A rock has ratio of Pb-206 to U-238 of 0.115. How old is it if t 1/2 of U-238 = 4.5 x 10 9 yrs ?
    • Strategy: figure out N/N 0 of U-238, then use the 2 previous equations to get . . .
    • 7.1 x 10 8 years . Calculations . . .
    • Pb /U = 115/1000 so N 0 U238 = 1115, N = 1000
    • ln( 1000/1115 ) = -(0.693/ 4.5 x 10 9 ) t
  • 39. Nuclear Medicine
    • Radioisotope Tracers
      • absorbed by specific organs and used to diagnose diseases
    • Radiation Treatment
      • larger doses are used to kill cancerous cells in targeted organs
      • internal or external radiation source
    Radiation treatment using  -rays from cobalt-60.
  • 40. Other Uses
    • Food Irradiation
      •  radiation is used to kill bacteria
    • Radioactive Tracers
      • explore chemical pathways
      • trace water flow
      • study plant growth, photosynthesis
    • Consumer Products
      • ionizing smoke detectors - 241 Am
  • 41. Radioisotopes Used As Tracers
  • 42. 18.5 Thermodynamic Stability of the Nucleus
    • Mass Defect - difference from mass of an atom & the mass of its individual particles.
    4.00260 amu 4.03298 amu
  • 43. Nuclear Binding Energy
    • Energy released when a nucleus is formed from nucleons.
    • High binding energy = stable nucleus.
    E = mc 2 E: energy (J) m: mass defect ( kg ) c: speed of light (3.00 x 10 8 m/s)
  • 44. Nuclear Binding Energy
    • Unstable nuclides - radioactive & undergo radioactive decay.
    • Elements with intermediate atomic masses ( e.g. , Fe) have greatest binding energy, so are the most stable .
  • 45. 18.6 Nuclear Fission and Nuclear Fusion Fission - splitting Fusion - Combining Both produce more stable nuclides so they are exothermic processes
  • 46. A. Nuclear Fission
    • Splitting a nucleus into two or more smaller nuclei
    • 1 g of 235 U = 3 tons of coal
  • 47. Nuclear Fission
    • Fission
    • large nuclei break up
    • 235 U + 1 n 139 Ba + 94 Kr + 3 1 n +
    • 92 0 56 36 0
    Energy
  • 48. Nuclear Power
    • Fission Reactors
    Cooling Tower
  • 49. Schematic of the reactor core.
  • 50. Nuclear Power
    • Fission Reactors
  • 51. Fission
    • chain reaction - self-propagating reaction
    • critical mass - mass required to sustain a chain reaction
  • 52.  
  • 53. Nuclear Fusion
    • combining of two nuclei to form one nucleus of larger mass
    • thermonuclear reaction – requires temp of 40,000,000 K to sustain
    • 1 g of fusion fuel = 20 tons of coal (vs. 3 in fission)
    • occurs naturally in stars
  • 54. Nuclear 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
  • 55. Nuclear Power
    • Fusion Reactors (not yet sustainable)
  • 56. Nuclear Power
    • Fusion Reactors (not yet sustainable)
    Tokomak Fusion Test Reactor Princeton University National Spherical Torus Experiment
  • 57. Fission vs. Fusion pp
    • 235 U is limited
    • danger of meltdown
    • toxic waste
    • thermal pollution
    • fuel is abundant
    • no danger of meltdown
    • no toxic waste
    • not yet sustainable
    FISSION FUSION
  • 58. Learning Check NR4
    • Indicate if each of the following are
    • Fission (2) fusion
    • Nucleus splits
    • Large amounts of energy released
    • Small nuclei form larger nuclei
    • Hydrogen nuclei react
    Energy
  • 59. Solution NR4
    • Indicate if each of the following are
    • Fission (2) fusion
    • 1 Nucleus splits
    • 1 + 2 Large amounts of energy released
    • 2 Small nuclei form larger nuclei
    • 2 Hydrogen nuclei react
  • 60. E. Nuclear Weapons
    • Atomic Bomb
      • chemical explosion is used to form a critical mass of 235 U or 239 Pu
      • fission develops into an uncontrolled chain reaction
    • Hydrogen Bomb
      • chemical explosion  fission  fusion
      • fusion increases the fission rate
      • more powerful than the atomic bomb
  • 61. 18.7 Effects of Radiation pp
    • Somatic - damage to the organism causing sickness or death.
    • Genetic - damage to the genetic machinery causing birth defects.
  • 62. Factors for Biological Effects of Radiation pp
    • Energy - higher energy content (rads) causes more damage.
    • Penetrating Ability -  >  - > 
    • Ionizing Ability -  >  - >  (eating an  -particle producer like Pu is very deadly)
    • Chemical Properties
      • Kr-85 is chemically inert, passes through quickly
      • Sr-90 collects in bone and stays a long time in the body.
  • 63.  
  • 64. Radioactive particles and rays vary greatly in penetrating power.
  • 65.  
  • 66. Diagram for the tentative plan for deep underground isolation of nuclear waste .