Nuclear Chemistry Powerpoint

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Nuclear Chemistry Powerpoint

  1. 1. Nuclear Chemistry<br />
  2. 2. Radioactivity – spontaneous emission of particles and or radiation<br />(proposed by Marie Curie)<br /><ul><li>Three types of ray are produced by the decay, or breakdown, of radioactive</li></ul> substances<br /> A. Alpha rays ( α ) – consist of positively charged particles called alpha particles and therefore are deflected by the positively charged plate.<br /> B. Beta rays ( β ) – or beta particles – are electrons and deflected by negatively charged plate<br /> C. Gamma rays ( γ ) – have no charged and are not affected by an external electric field or magnetic field<br />
  3. 3. Lead block<br />Radioactive substance<br />–<br />a<br />g<br />b<br />+<br />
  4. 4. Lead block<br />–<br />+<br />
  5. 5. Lead block<br />Radioactive substance<br />–<br />a<br />+<br />
  6. 6. Lead block<br />Radioactive substance<br />–<br />b<br />+<br />
  7. 7. Lead block<br />g<br />Radioactive substance<br />–<br />+<br />
  8. 8. Lead block<br />Radioactive substance<br />–<br />a<br />g<br />b<br />+<br />
  9. 9.
  10. 10. A<br />X<br />Mass Number<br />Element Symbol<br />Z<br />Atomic Number<br />a particle<br />proton<br />neutron<br />electron<br />positron<br />or<br />or<br />1p<br />1H<br />0b<br />0e<br />or<br />1<br />1<br />+1<br />1n<br />0e<br />+1<br />0b<br />0<br />-1<br />-1<br />4a<br />4He<br />or<br />2<br />2<br />Atomic number (Z) = number of protons in nucleus<br /> Mass number (A) = number of protons + number of neutrons <br /> = atomic number (Z) + number of neutrons<br />A<br />1<br />1<br />0<br />0<br />4<br />1<br />0<br />-1<br />+1<br />2<br />Z<br />23.1<br />
  11. 11. +<br />+<br />+ 2<br />+<br />+<br />+ 2<br />1n<br />1n<br />1n<br />1n<br />96<br />96<br />0<br />0<br />0<br />0<br />Rb<br />Rb<br />37<br />37<br />235<br />138<br />235<br />138<br />U<br />Cs<br />U<br />Cs<br />92<br />55<br />92<br />55<br />Balancing Nuclear Equations<br />Conserve mass number (A). <br />The sum of protons plus neutrons in the products must equal the sum of protons plus neutrons in the reactants.<br />235 + 1 = 138 + 96 + 2x1<br />Conserve atomic number (Z) or nuclear charge. <br />The sum of nuclear charges in the products must equal the sum of nuclear charges in the reactants.<br />92 + 0 = 55 + 37 + 2x0<br />23.1<br />
  12. 12. or<br />alpha particle - <br />212Po 4He + AX<br />2<br />Z<br />84<br />212Po 4He + 208Pb<br />2<br />82<br />84<br />4a<br />4He<br />2<br />2<br />212Po decays by alpha emission. Write the balanced nuclear equation for the decay of 212Po.<br />212 = 4 + A<br />A = 208<br />84 = 2 + Z<br />Z = 82<br />23.1<br />
  13. 13. 23.1<br />
  14. 14. I. Nuclear Stability and Radioactive Decay<br />
  15. 15. X<br />Y<br />n/p too large<br />beta decay<br />n/p too small<br />positron decay or electron capture<br />23.2<br />
  16. 16.
  17. 17.
  18. 18. Predicting the mode of decay<br />High n/p ratio (too many neutrons; lie above band of stability) --- undergoes beta decay <br /> Low n/p ratio (neutron poor; lie below band of stability) --- positron decay or electron capture<br />Heavy nuclides ( Z &gt; 83) --- alpha decay<br />
  19. 19. II. Nuclear Transmutations<br /><ul><li>Nuclear reactions that are induced in a way that nucleus is struck by a neutron or by another nucleus (nuclear bombardment) </li></ul>Positive ion bombardment<br /> - alpha particle is the most commonly used positive ion<br />- uses accelerators<br />Examples:<br />147 N + 42 He -> 178 O + 11H<br /> 94Be + 42 He -> 126 C + 10n<br />Neutron bombardment<br /> - neutron is bombarded to a nucleus to form a new nucleus<br />- most commonly used in the transmutation to form synthetic isotopes because neutron are neutral, they are not repelled by nucleus<br />Example:<br /> 5826 Fe + 10 n -> 5926 Fe -> 5927 Co + 0-1 e<br />
  20. 20. 5<br /> +<br /> +<br />+<br />+<br />+ 0-1 e<br />+<br />+<br />4He<br />1n<br />1n<br />0e<br />14N<br />1n<br />2<br />0<br />-1<br />7<br />0<br />0<br />239<br />242<br />238<br />239<br />239<br />239<br />238<br />247<br />Pu<br />Cm<br />U<br />U<br />Pu<br />Np<br />U<br />Es<br />94<br />96<br />92<br />92<br />94<br />93<br />92<br />99<br />Transuranium elements<br /><ul><li>Element with atomic numbers above 92
  21. 21. Produced using artificial transmutations, either by:</li></ul>alpha bombardment<br />neutron bombardment<br />bombardment from other nuclei<br />Examples:<br />a. <br />b. <br />c. <br />
  22. 22. III. Nuclear Energy<br />Recall:<br />Nucleus is composed of proton and neutron<br />Then, is the mass of an atom equal to the total mass of all the proton plus the total mass of all the neutron?<br />Example for a He atom:<br />Total mass of the subatomic particles<br />= mass of 2 p+ + mass of 2n0<br />= 2 ( 1.00728 amu ) + 2 (1.00867 amu)<br />= 4.03190 amu<br />And atomic weight of He-4 is 4.00150<br />Why does the mass differ if the atomic mass = number of protons + number of neutrons?<br />
  23. 23. Mass defect<br />-mass difference due to the release of energy<br />-this mass can be calculated using Einstein’s equation E =mc2<br />2 11 H + 2 20 H -> 42 He + energy<br />Therefore:<br />-energy is released upon the formation of a nucleus from the constituent protons and neutrons<br />-the nucleus is lower in energy than the component parts.<br />-The energy released is a measure of the stability of the nucleus. Taking the reverse of the equation:<br /> 42He + energy -> 2 11 H + 2 20 n<br />
  24. 24. Therefore,<br />-energy is released to break up the nucleus into its component parts. This is called the nuclear binding energy.<br />-the higher the binding energy, the stable the nuclei.<br />-isotopes with high binding energy and most stable are those in the mass range 50-60.<br />
  25. 25. Nuclear binding energy per nucleon vs Mass number<br />nuclear binding energy<br />nucleon<br />nuclear stability<br />23.2<br />
  26. 26. -The plot shows the use of nuclear reactions as source of energy.<br />-energy is released in a process which goes from a higher energy state (less stable, low binding energy) to a low energy state (more stable, high binding energy).<br />-Using the plot, there are two ways in which energy can be released in nuclear reactions:<br />a. Fission – splitting of a heavy nucleus into smaller nuclei<br />b. Fusion – combining of two light nuclei to form a heavier, more stable nucleus.<br />
  27. 27. BE + 19F 91p + 101n<br />0<br />9<br />1<br />binding energy per nucleon = <br />binding energy<br />number of nucleons<br />2.37 x 10-11 J<br />19 nucleons<br />= <br />Nuclear binding energy (BE) is the energy required to break up a nucleus into its component protons and neutrons.<br />E = mc2<br />BE = 9 x (p mass) + 10 x (n mass) – 19F mass<br />BE (amu) = 9 x 1.007825 + 10 x 1.008665 – 18.9984<br />BE = 0.1587 amu<br />1 amu = 1.49 x 10-10 J<br />BE = 2.37 x 10-11J<br />= 1.25 x 10-12 J<br />23.2<br />
  28. 28. 23.3<br />
  29. 29. 14N + 1n 14C + 1H<br />0<br />7<br />1<br />6<br />14C 14N + 0b + n<br />6<br />7<br />-1<br />238U 206Pb + 8 4a + 6 0b<br />92<br />-1<br />82<br />2<br />Radiocarbon Dating<br />t½ = 5730 years<br />Uranium-238 Dating<br />t½ = 4.51 x 109 years<br />23.3<br />
  30. 30. 14N + 4a17O + 1p<br />7<br />2<br />1<br />8<br />27Al + 4a30P + 1n<br />13<br />2<br />0<br />15<br />14N + 1p 11C + 4a<br />7<br />1<br />2<br />6<br />Cyclotron Particle Accelerator<br />Nuclear Transmutation<br />23.4<br />
  31. 31. Nuclear Transmutation<br />23.4<br />
  32. 32. 235U + 1n 90Sr + 143Xe + 31n + Energy<br />38<br />0<br />0<br />54<br />92<br />Nuclear Fission<br />Energy = [mass 235U + mass n – (mass 90Sr + mass 143Xe + 3 x mass n )] x c2<br />Energy = 3.3 x 10-11J per 235U<br />= 2.0 x 1013 J per mole 235U<br />Combustion of 1 ton of coal = 5 x 107 J<br />23.5<br />
  33. 33. 235U + 1n 90Sr + 143Xe + 31n + Energy<br />38<br />0<br />0<br />54<br />92<br />Nuclear Fission<br />Representative fission reaction<br />23.5<br />
  34. 34. Non-critical<br />Critical<br />Nuclear Fission<br />Nuclear chain reaction is a self-sustaining sequence of nuclear fission reactions.<br />The minimum mass of fissionable material required to generate a self-sustaining nuclear chain reaction is the critical mass.<br />23.5<br />
  35. 35. Nuclear Fission<br />Schematic diagram of a nuclear fission reactor<br />23.5<br />
  36. 36. 35,000 tons SO2<br />4.5 x 106 tons CO2<br />70 ft3 vitrified waste<br />3.5 x 106 <br />ft3 ash<br />1,000 MW coal-fired<br />power plant<br />1,000 MW nuclear<br />power plant<br />Nuclear Fission<br />Annual Waste Production<br />23.5<br />
  37. 37. Nuclear Fission<br />Hazards of the radioactivities in spent fuel compared to uranium ore<br />23.5<br />From “Science, Society and America’s Nuclear Waste,” DOE/RW-0361 TG<br />
  38. 38. 2H + 2H 3H + 1H<br />1<br />1<br />1<br />1<br />2H + 3H 4He + 1n<br />2<br />1<br />0<br />1<br />6Li + 2H 2 4He<br />2<br />3<br />1<br />Nuclear Fusion<br />Fusion Reaction<br />Energy Released<br />6.3 x 10-13 J<br />2.8 x 10-12 J<br />3.6 x 10-12 J<br />Tokamak magnetic plasma confinement<br />23.6<br />
  39. 39. Radioisotopes in Medicine<br /><ul><li>1 out of every 3 hospital patients will undergo a nuclear medicine procedure
  40. 40. 24Na, t½ = 14.8 hr, b emitter, blood-flow tracer
  41. 41. 131I, t½ = 14.8 hr, b emitter, thyroid gland activity
  42. 42. 123I, t½ = 13.3 hr, g-ray emitter, brain imaging
  43. 43. 18F, t½ = 1.8 hr, b+ emitter, positron emission tomography
  44. 44. 99mTc, t½ = 6 hr, g-ray emitter, imaging agent</li></ul>Brain images with 123I-labeled compound<br />23.7<br />
  45. 45. Geiger-Müller Counter<br />23.7<br />
  46. 46. Biological Effects of Radiation<br />Radiation absorbed dose (rad)<br />1 rad = 1 x 10-5 J/g of material<br />Roentgen equivalent for man (rem)<br />1 rem = 1 rad x Q<br />Quality Factor<br />g-ray = 1<br />b = 1<br />a = 20<br />23.8<br />
  47. 47. Chemistry In Action: Food Irradiation<br />

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