1 Nuclear Chemistry
2 Units for Measuring Radiation Curie: 1 Ci = 3.7 x distintegrations/s SI unit is the becquerel: 1 Bq = 1 dps Rad: measures amount of energy absorbed 1 rad = 0.01 J absorbed/kg tissue Rem: based on rad and type of radiation. Quantifies biological tissue damage Usually use “millirem”
3 Chronic Radiation Exposure
4 Effects of Acute Radiation
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6 Half-Life Section 15.4 & Screen 15.8 HALF-LIFE is the time it takes for 1/2 a sample is disappear.HALF-LIFE is the time it takes for 1/2 a sample is disappear. The rate of a nuclear transformation depends only on the “reactant” concentration.The rate of a nuclear transformation depends only on the “reactant” concentration. Concept of HALF-LIFE is especially useful for 1st order reactions.Concept of HALF-LIFE is especially useful for 1st order reactions.
7 Half-Life Decay of 20.0 mg of 15 O. What remains after 3 half-lives? After 5 half-lives?
8 Kinetics of Radioactive Decay Activity (A) = Disintegrations/time = (k)(N) where N is the number of atoms Decay is first order, and so ln (A/A o ) = -kt The half-life of radioactive decay is t 1/2 = 0.693/k
9 Carbon-14 Dating
10 Radiocarbon Dating Radioactive C-14 is formed in the upper atmosphere by nuclear reactions initiated by neutrons in cosmic radiation 14 N + 1 o n ---> 14 C + 1 H The C-14 is oxidized to CO 2, which circulates through the biosphere. When a plant dies, the C-14 is not replenished. But the C-14 continues to decay with t 1/2 = 5730 years. Activity of a sample can be used to date the sample.
11 Transuranium Elements & Glenn Seaborg 106 Sg
12 Transuranium Elements Elements beyond 92 (transuranium) made starting with an n, reaction U n ---> U + U ---> Np Np ---> Pu Np ---> Pu
13 FUSION and FISSION: Nuclear Weapons
14 Nuclear Reactions Natural decay –Alpha –Beta Fusion (together) Fission (break apart)
15 Nuclear Fusion The process in which small nuclei combine at extremely high temperatures, forming larger nuclei and releasing energy.
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18 Fusion: Adv / Disad. Great weapon because releases large amounts of energy Can make new elements with atomic numbers greater than 92 NOT used for Nuclear energy because not able to control reaction (Energy in greater than energy out)
19 Nuclear Fission
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21 Nuclear Fission & Lise Meitner 109 Mt
22 Nuclear Bomb: Fission Nuclear Chain Reaction Critical Mass
23 1.Initiation. Reaction of a single atom starts the chain (e.g., U + neutron) (e.g., 235 U + neutron) 2. Propagation. U fission releases neutrons that initiate other fissions 2. Propagation. 236 U fission releases neutrons that initiate other fissions 3. Termination.
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25 Fission: Adv / Disad. Great weapon because releases large amounts of energy Used for Nuclear energy because CAN control reaction Dis: Nuclear waste and radiation generated
26 Nuclear Fission & POWER Currently about 103 nuclear power plants in the U.S. and about 435 worldwide.Currently about 103 nuclear power plants in the U.S. and about 435 worldwide. 17% of the world’s energy comes from nuclear.17% of the world’s energy comes from nuclear.
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28 Nuclear Power: Advantages More power for less amount of fuel Non-air polluting
29 Nuclear Power: disadvantages Nuclear Power: disadvantages Radioactive waste. Waste disposal Possibility of melt-down 30 year operational life.
30 Nuclear Medicine: Imaging Nuclear Medicine: Imaging Radioactive isotopes are used to diagnosis and treat diseases Thyroid imaging using Tc-99m IF RADIATION IS BAD FOR YOU WHY INTENTIONALLY EXPOSE YOURSELF?
31 Nuclear Medicine: Imaging Technetium-99m is used in more than 85% of the diagnostic scans done in hospitals each year. Synthesized on-site from Mo Mo ---> 99m 43 Tc 99m 43 Tc decays to Tc giving off ray. Tc-99m contributes in sites of high activity.
32 Nuclear Medicine: Imaging
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34 Nuclear Radiation: Beneficial Nuclear Radiation: Beneficial Can be used to treat cancer Can be used as tracers in agriculture, medicine, and scientific research.
35 Food Irradiation Gamma radiation from Cobalt-60
36 Smoke Detectors
37 Medical Imaging
38 PET SCANNER
39 PET SCAN IMAGES