Nuclear Chemistry Chapter 25. Radiation In 1896, Antoine Henri Becquerel discovered radiation by accident. His associates at the time were Marie and Pierre

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Nuclear Chemistry Chapter 25 Slide 2 Radiation In 1896, Antoine Henri Becquerel discovered radiation by accident. His associates at the time were Marie and Pierre Curie. Marie Curie gets credit for naming radioactivity. Slide 3 Radioisotopes Nuclei of unstable isotopes are called radioisotopes. An unstable nucleus releases energy by emitting radiation during the process of radioactive decay Slide 4 Radiation Three Types Alpha Helium Nucleus Beta Electron Gamma Light wave Slide 5 Symbols Alpha Gamma Beta Slide 6 Radiation Slide 7 Slide 8 Nuclear Symbols Table O Slide 9 Nuclear Stability For smaller atoms a ratio of 1:1 neutrons to protons helps to maintain stability C-12, N-14, O-16 For larger atoms, more neutrons than protons are required to maintain stability Pb-207, Au-198, Ta-181 Slide 10 Nuclear Stability Slide 11 Radioactive Decay Radioisotopes will undergo decay reactions to become more stable Alpha Decay Beta Decay Positron Emission Slide 12 Nuclear Reactions Unstable isotopes of one element are transformed into stable isotopes of a different element. They are not affected by outside factors, like temp and pressure. They can not be sped up or slowed down. Slide 13 General Reaction Format ReactantsProducts Starting MaterialEnding Material Science equivalent of Maths = Slide 14 Reaction Format In Math class you might say: A B = C In Science, we dont use subtraction A B + C A breaks into B and C Slide 15 Decay Reactions Decay reactions involve one unstable nuclei decaying (breaking down) into 2 (or more) smaller nuclei. Alpha Decay - one of the products is an alpha particle Beta Decay - one of the products is a beta particle Slide 16 Nuclear Reactions Reactions must always Balance Mass Numbers have to balance Atomic Numbers have to balance 238 = 4 + 234 92 = 2 + 90 Slide 17 Alpha Decay Slide 18 Slide 19 Slide 20 Beta Decay Slide 21 Slide 22 Slide 23 Positron Emission Slide 24 Slide 25 Transmutations Any reaction where one element is transformed into a different element Two main types Natural Artificial Slide 26 Transmutations Natural Usually has one reactant Alpha and Beta Decay Artificial Usually has more than one reactant Particle Accelerators Slide 27 Example X Slide 28 X Slide 29 X Slide 30 Slide 31 Half Life Amount of time for half of a sample to decay into a new element Parent Atoms Undecayed atoms Daughter Atoms Decayed atoms Slide 32 Half Life Number of Half- lives Fraction left 01 11/2 21/4 31/8 41/16 51/32 Slide 33 Half Life Number of half-lives t = amount of time elapsed T = half-life Slide 34 Example How many half lives does it take for a sample of C-14 to be 11460 yrs old? Slide 35 Half Life Fraction Remaining t = amount of time elapsed T = half-life Slide 36 Example What fraction of P-32 is left after 42.9days? Slide 37 Example How long will a sample of Rn-222 take to decay down to 1/4 of the original sample? 7.64d Slide 38 Fraction Remaining Mass Left Original Mass = Slide 39 Practice How much Carbon-14 was originally in a sample that contains 4g of C-14 and is 17190 years old? 32g Slide 40 More Practice How much 226 Ra will be left in a sample that is 4800 years old, if it initially contained 408g? 51g Slide 41 And One More. What is the half life of a sample that started with 144g and has only 9g left after 28days? 7d Slide 42 Slide 43 Fission Splitting of a larger atom into two or more smaller pieces Nuclear Power Plants One Example: Slide 44 Fission Slide 45 Energy Production Energy is produced by a small amount of mass being converted to energy E=mc 2 Slide 46 Chain Reaction Reaction that produces material that can initiate more than one reaction Slide 47 Chain Reaction Slide 48 Fusion Joining of two or more smaller pieces to make a larger piece Sun, Stars One Example: Slide 49 More Examples: Fusion Slide 50 Slide 51 Energy Production Energy is produced by a small amount of mass being converted to energy More energy is produced by fusion than any other source E=mc 2 Slide 52 Fission vs. Fusion Advantages of Fission Produces a lot of energy Can be a controlled reaction Material is somewhat abundant Slide 53 Fission vs. Fusion Disadvantages of Fission Uses hazardous material Produces hazardous material Long Half Life Reaction can run out of control. Limited amount of fissionable material Slide 54 Fission vs. Fusion Advantages of Fusion Lighter weight material Easily available material Produces waste that is lighter and has shorter half-life Produces more energy than fission Slide 55 Fission vs. Fusion Disadvantages of Fusion Must be done at very high temperatures Only been able to attain 3,000,000K Have not been able to sustain stable reaction for energy production Slide 56 Slide 57 Uses of Radioisotopes Smoke Detectors Food Irradiation Radioactive Dating Medical Tracers Nuclear Power Plants Nuclear Weapons Origin of Elements Slide 58 Smoke Detectors Americium produces radiation that is monitored by an electrical circuit Smoke interferes with the current, triggering the alarm Slide 59 Food Irradiation Food is exposed to radiation, killing bacteria and mold Food is cleaner and lasts longer Slide 60 Radioactive Dating Ratio of Parent atoms to Daughter atoms provides an age Examples C-14 used to date organic material U-238 used to date geological formations Slide 61 Medical Tracers Radioisotopes replace stable isotopes Radiation produced can be detected by machines Example I-131 is used for thyroid disorders Barium milk shakes Co-60 for Cancer Slide 62 Radioisotopes You must know these radioisotopes and uses I-131 Diagnosing and treating thyroid disorders Co-60 Treating cancer Slide 63 Radioisotopes You must know these radioisotopes and uses C-14 Dating living organisms Compare to C-12 U-238 Dating geologic formations Compare to Pb-206 Slide 64 Nuclear Power Plants Slide 65 Slide 66 Slide 67 Nuclear Weapons Slide 68 Video Origin of Elements YouTube Slide 69 Stability Elements 1-26 are made in the core of stars Elements 27-92, excluding 43 and 61, are made during a Supernova explosion No element larger than 83 has a stable isotope No element larger than 92 is made in nature

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