1. Chapter 20 Nuclear Chemistry Insert picture from First page of chapter

2. Copyright McGraw-Hill 20092 20.1 Nuclei and Nuclear Reactions Radioactive decay – emission of particles and/or electromagnetic radiation by unstable nuclei Radioactivity - Spontaneous emission of particles or electromagnetic radiation Nuclear transmutation, results from the bombardment of nuclei by neutrons, protons, or other nuclei.

3. Copyright McGraw-Hill 20093 Radioactive decay and nuclear transmutation are nuclear reactions, which differ significantly from ordinary chemical reactions.

4. Copyright McGraw-Hill 20094 The symbols for subatomic particles are as follows: In balancing any nuclear equation, we must balance the total of all atomic numbers and the total of all mass numbers for the products and reactants.

5. Copyright McGraw-Hill 20095 Identify X in the following nuclear equation.

6. Copyright McGraw-Hill 20096  reactant mass numbers =  product mass numbers  reactant atomic numbers =  product atomic numbers Therefore, X is Se or

7. Copyright McGraw-Hill 20097 20.2 Nuclear Stability Nuclear stability determined by a balance between –Coulombic repulsions –Short range nuclear attractions (very strong) –If replusions > attractions, the nucleus is unstable –If attractions > replusions, the nucleus is stable

8. Copyright McGraw-Hill 20098 Patterns of nuclear stability –Nuclei containing a magic number of protons and/or neutrons are stable. The numbers 2, 8, 20, 50, 82, and 126 are called magic numbers. –There are many more stable nuclei with even numbers of both protons and neutrons than with odd numbers of these particles. –All isotopes of the elements with atomic numbers higher than 83 are radioactive. –All isotopes of technetium (Tc, Z = 43) and promethium (Pm, Z = 61) are radioactive.

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10. 10  particle emission electron capture positron emission Above the belt Below the belt

11. Copyright McGraw-Hill 200911 Nuclear Binding Energy –Quantitative measure of nuclear stability –The energy required to break up a nucleus into its component protons and neutrons. –Represents the conversion of mass to energy that occurs during an exothermic nuclear reaction. –The difference between the mass of an atom and the sum of the masses of its protons, neutrons and electrons is called the mass defect.

12. Copyright McGraw-Hill 200912 –According to Einstein’s mass-energy equivalence relationship (E = mc 2, where E is energy, m is mass, and c is the velocity of light), the energy released is –where  E and  m are defined as follows:

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14. Copyright McGraw-Hill 200914 Calculate a) the nuclear binding energy in kilojoules/mol and b) the nuclear binding energy in joules per nucleon of. The exact atomic mass of bismuth is 208.9804.

15. Copyright McGraw-Hill 200915 a) Nuclear binding energy

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17. Copyright McGraw-Hill 200917 b) Nuclear binding energy per nucleon

18. Copyright McGraw-Hill 200918 20.3 Natural Radioactivity The disintegration of a radioactive nucleus often is the beginning of a radioactive decay series, which is a sequence of nuclear reactions that ultimately result in the formation of a stable isotope. The beginning radioactive isotope is called the parent and the product isotope is called the daughter.

19. Copyright McGraw-Hill 200919 Decay series for uranium-238

20. Copyright McGraw-Hill 200920 Kinetics of radioactive decay –First-order kinetics (N – number of radioactive nuclei at time t, k is the rate constant and is the half-life) –Used as the basis for dating ( 14 C and 238 U are used depending on material)

21. Copyright McGraw-Hill 200921 A piece of linen cloth found at an ancient burial site is found to have a 14 C activity of 4.8 disintegrations per minute. Determine the age of the cloth. Assume that the carbon-14 activity of an equal mass of living flax (the plant from which linen is made) is 14.8 disintegrations per minute. The half-life of carbon-14 is 5715 years.

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23. Copyright McGraw-Hill 200923 Uranium-238 Dating Compare to ratio found in sample.

24. Copyright McGraw-Hill 200924 20.4 Nuclear Transmutation Nuclear transmutation differs from radioactive decay in that transmutation is brought about by the collision of two particles. Particle accelerators made it possible to synthesize the so-called transuranium elements, elements with atomic numbers greater than 92.

25. Copyright McGraw-Hill 200925 Write an equation for the process represented by

26. Copyright McGraw-Hill 200926 emitted particlebombarding particle

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28. Copyright McGraw-Hill 200928 Schematic diagram of a cyclotron particle accelerator.

29. Copyright McGraw-Hill 200929 A particle accelerator uses electric and magnetic fields to increase the kinetic energy of charged species so that a reaction will occur.

30. Copyright McGraw-Hill 200930 20.5 Nuclear Fission Nuclear fission is the process in which a heavy nucleus (mass number > 200) divides to form smaller nuclei of intermediate mass and one or more neutrons. Because the heavy nucleus is less stable than its products, this process releases a large amount of energy.

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34. Copyright McGraw-Hill 200934 nuclear chain reaction, which is a self- sustaining sequence of nuclear fission reactions. critical mass, the minimum mass of fissionable material required to generate a self-sustaining nuclear chain reaction. Applications of nuclear fission –Atomic bomb –Generation of electricity

35. Copyright McGraw-Hill 200935 Critical Mass: Chain reaction occurs

36. Copyright McGraw-Hill 200936 Schematic diagram of an atomic bomb

37. Copyright McGraw-Hill 200937 Schematic Diagram of a Nuclear Fission Reactor

38. Copyright McGraw-Hill 200938 Refueling the Core of a Nuclear Reactor

39. Copyright McGraw-Hill 200939 Types of reactors (Using as fuel) –Light water reactor - uses H 2 O as moderator used to reduce kinetic energy of neutrons –Heavy water reactor – uses D 2 O as moderator More efficient than light water reactor –Breeder reactor – produces more fissionable fuel than it uses Doubling time – time to produce enough fuel to refuel the original reactor Can utilize fertile isotopes plutonium-239 and thorium-232

40. Copyright McGraw-Hill 200940 20.6 Nuclear Fusion Nuclear fusion - the combining of small nuclei into larger one –Exempt from waste disposal issues of fission Solar fusion Thermonuclear reactions – take place at very high temperatures

41. Copyright McGraw-Hill 200941 Promising reactions Technical difficulty – confine nuclei at required temperatures –Magnetic confinement –High-power lasers

42. Copyright McGraw-Hill 200942 Tokamak : A magnetic plasma confinement design

43. Copyright McGraw-Hill 200943 Used in hydrogen (thermonuclear) bombs –High temperatures attained –Contain solid LiD –Cleaner than fission bombs

44. Copyright McGraw-Hill 200944 20.7 Use of Isotopes Chemical analysis –Use of tracers Sulfur-35 in the determination of the structure of thiosulfate Photosynthetic pathway using oxygen-18 and 14-carbon

45. Copyright McGraw-Hill 200945 Isotopes in medicine –Use of tracers for diagnosis Sodium-24 – blood flow Iodine-131 –thyroid conditions Iodine -123 – brain imaging –Major advantage – easy to detect normal Alzheimer victim

46. Copyright McGraw-Hill 200946 Geiger Counter: Used to detect radiation

47. Copyright McGraw-Hill 200947 20.8 Biological Effects of Radiation Quantitative measures of radation –curie (Ci): fundamental unit of radioactivity Equivalent to 3.70 x 10 10 nuclear disintegrations per second –rad (radiation absorbed dose) Considers activity Considers energy Considers type of radiation emitted 1 rad = 1 x 10  5 J/g of tissue irradiated

48. Copyright McGraw-Hill 200948 –RBE (relative biological effectiveness) Considers biological effect of radiation –Part of body irradiated –Type of radiation –rem (roentgen equivalent for man) Chemical basis for radiation damage –Ionizing radiation produces radicals –Radicals (free radicals) – molecular fragments with unpaired electrons

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50. Copyright McGraw-Hill 200950 –e  and the hydroxyl radical can form other radicals –In tissues radicals can attack and destroy membranes, enzymes, DNA, etc. Radiation damage –Somatic (affect the organism within its lifetime) –Genetic (inheritable changes and gene mutations)

51. Key Points Nuclei and nuclear reactions –Radioactive decay –Nuclear transmutations –Particles involved in nuclear reactions –Balancing nuclear reactions Nuclear stability –Type of interactions involved –Pattern of stability

52. Magic numbers Odd/even numbers of nucleons –Nuclear binding energy Mass defect Einstein’s mass-energy equivalence relationship Calculation nuclear binding energy –Per mole of nucleons –Per nucleon Natural radioactivity –Radioactive decay series

53. –Kinetics of radioactive decay –Dating based on radioactive decay Carbon-14 dating Uranium-238 dating Potassium-40 dating Nuclear Transmutation –Transuranium element –Particle accelerators Nuclear fission –Nuclear fission reactions

54. Nuclear chain reactions Critical mass –Generation of electric power Light water reactors Heavy water reactors Breeder reactors –Nuclear fusion Solar nuclear reactions Thermonuclear reactions Potential for generation of electric power Thermonuclear bombs

55. Uses of Isotopes –Chemical Analysis –Medicine Biological effects of radiation –Units to measure radiation curie rad RBE rem –Effect of free radicals –Somatic damage –Genetic damage