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Outline: 4/18/07

Outline: 4/18/07. Avg: 7.2. Pick up Quiz 9 – from me Special seminar Wednesday 7:30pm & Thursday 3pm Last two seminars: Friday @ 4pm. Today: Chapter 22 (cont’d). Nuclear Chemistry - Common decay calcs - Biological interactions. Let do some CAPA questions:.

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Outline: 4/18/07

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  1. Outline: 4/18/07 Avg: 7.2 • Pick up Quiz 9 – from me • Special seminar Wednesday 7:30pm & Thursday 3pm • Last two seminars: Friday @ 4pm Today: Chapter 22 (cont’d) Nuclear Chemistry - Common decay calcs - Biological interactions

  2. Let do some CAPA questions: • Mono-isotopic: only one isotope • It weighs: 26.982 g/mol (per. table) #4 – What’s the binding energy of 27Al? • Add up the masses of the protons & neutrons & electrons, and subtract the total mass of the individual constituents from the actual mass of the isotope.

  3. Let do some CAPA questions: How many protons? • 13 #4 – What’s the binding energy of 27Al? How many neutrons? • 14 How many electrons? • 13 • Table 22-1 (p. 944): 131.007276 + 141.008665 + 130.000549 = 27.223 g/mol • Difference: =26.982 - 27.223 g/mol =-0.241 g/mol  8.988e10 kJ/g = -2.17e10 kJ/mol

  4. How does this compare to chemical energies? • Explosion of tri-nitro-toluene (TNT) has a DH of 1026 kJ/mol… • The amount of energy used to hold together 1 mole of Al nuclei is: 21700000000 kJ/mol…

  5. Binding Energy per Nucleon

  6. Let do some CAPA questions: • 1.0-1.5 Check proton-to-neutron ratio #8 – Which are the stable isotopes? Check for odd-odd p & n Check for heavies (Z>83) Check for artificial elements (Tc, 3H)

  7. 0.143 mol 14C  6.022e23 atoms/mol • = 8.60e21 atoms 14C Worksheet #13 - Question 2 • 0.02% of 1000g = • 0.2 g 14C • 0.2 g  1mol/14g = 0.143 mol 14C • N/N0 = 7.65e20 / 8.60e21 = 0.0889 • ln (0.0889) = - k t • - 2.42 = - 1.209 × 10-4 yr-1 t • t = 20,000 yr

  8. N = ? • N = 7.65e20e- kt • 7.65e20 e - 1.209 × 10-4 (1/52) Worksheet #13 - Question 3 • 7.65e20 14C atoms = • N0 • t = 1/52 yr • N = 7.64998e20 N- N0 = 1.78e15

  9. a b g Why a thin layer? High energy, sub-atomic (small) : highly penetrating High energy: highly ionizing

  10. What effect does it have on biology? Penetrating, ionizing…..

  11. Why is too much radiation bad for living things?

  12. case 2: DNA - single ionization  radiation ionizes & breaks the strand on one side - but the DNA repairs itself case 1: a cell  radiation ionizes the cell wall or other parts and kills the cell

  13. case 3: DNA - multiple ionization   rearrangements are possible - a mutation occurs radiation ionizes & breaks the strand - DNA fragments

  14. case 4: DNA - multiple ionization Since break-points are far away, DNA repairs itself   radiation ionizes & breaks the strand

  15. What affect does it have on biology? Mutation….mutagenisis, Cancer….tumorigenisis. Does it make atoms radioactive? No…ionization is a chemical process, not a nuclear process.

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