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Nuclear Chemistry Types of Radiation Nuclear Decay Half-LifeApplications Big Bang Movie Big Bang Movie Types of Radiation Nuclear Decay Half-LifeApplications Big Bang Movie Big Bang Movie I IV III II
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A. Types of Radiation Alpha particle ( ) helium nucleus Alpha Particle movie Alpha Particle movie paper 2+ Beta particle ( -) electron 1- lead Positron ( +) positron 1+ Gamma ( ) high-energy photon Radiation movie Radiation movie 0 concrete
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B. Nuclear Decay Alpha Emission parent nuclide daughter nuclide alpha particle Numbers must balance!!
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B. Nuclear Decay Beta Emission electron Positron Emission positron
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B. Nuclear Decay Electron Capture electron Gamma Emission Usually follows other types of decay. Transmutation One element becomes another.
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Band of Stability Atoms give off radiation in an attempt to increase stability. Stability is determined by the ratio of protons to neutrons. The neutron/proton ration needs to be between 1.0 and 1.5
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B. Nuclear Decay Why nuclides decay… need stable ratio of neutrons to protons DECAY SERIES TRANSPARENCY
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Neutron to Proton Ratio
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Uranium-238 Decay Series
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C. Half-life Half-life (t ½ ) Time required for half the atoms of a radioactive nuclide to decay. Shorter half-life = less stable.
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C. Half-life m f :final mass m i :initial mass n:# of half-lives n = t/T 1/2 t: total time elapsed T 1/2 : length of half life
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C. Half-life Fluorine-21 has a half-life of 5.0 seconds. If you start with 25 g of fluorine-21, how many grams would remain after 60.0 s? GIVEN: t ½ = 5.0 s m i = 25 g m f = ? total time = 60.0 s n = 60.0s ÷ 5.0s =12 WORK : m f = m i (½) n m f = (25 g)(0.5) 12 m f = 0.0061 g
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Nuclear Chemistry Fission & Fusion Fission & Fusion Domino Movie Domino Movie Fission & Fusion Fission & Fusion Domino Movie Domino Movie I IV III II
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A. F ission splitting a nucleus into two or more smaller nuclei 1 g of 235 U = 3 tons of coal
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A. F ission chain reaction - self-propagating reaction
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Critical Mass critical mass - mass required to sustain a chain reaction Domino Unveiling MovieDomino Unveiling Movie
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B. Fusion combining of two nuclei to form one nucleus of larger mass thermonuclear reaction – requires temp of 40,000,000 K to sustain 1 g of fusion fuel = 20 tons of coal occurs naturally in stars
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C. Fission vs. Fusion 235 U is limited danger of meltdown toxic waste thermal pollution fuel is abundant no danger of meltdown no toxic waste not yet sustainable FISSIONFISSION FUSIONFUSION
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Nuclear Chemistry ApplicationsApplications I IV III II
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A. Nuclear Power Fission Reactors- control rods are critical Cooling Tower
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A. Nuclear Power Fission Reactors moviemovie
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A. Nuclear Power Fusion Reactors (not yet sustainable)
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A. Nuclear Power Fusion Reactors (not yet sustainable) Tokamak Fusion Test Reactor Princeton University National Spherical Torus Experiment
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A. Nuclear Power Nuclear Power is relatively safe today; but when accidents occur, the damage can be devastating as Chernobyl demonstrated. Boron control rods are used to regulated the chain reaction by absorbing neutrons.
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B. Synthetic Elements Transuranium Elements elements with atomic #s above 92 synthetically produced in nuclear reactors and accelerators most decay very rapidly
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B. Synthetic Elements The main Tevatron ring has a diameter of more than 0.8 km and a circumference of about 6.4 km. It uses conventional and superconducting magnets to accelerate particles to high speeds and energies.
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C. Radioactive Dating half-life measurements of radioactive elements are used to determine the age of an object moviemovie decay rate indicates amount of radioactive material EX: 14 C - up to 60,000 years 238 U and 40 K - over 300,000 years
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D. Nuclear Medicine Radiation Treatment larger doses are used to kill cancerous cells in targeted organs internal or external radiation source Radiation treatment using -rays from cobalt-60.
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D. Nuclear Medicine Radioisotope Tracers absorbed by specific organs and used to diagnose diseases movie movie Show DVD Isotope Tracers
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E. Nuclear Weapons Atomic Bomb chemical explosion is used to form a critical mass of 235 U or 239 Pu fission develops into an uncontrolled chain reaction Hydrogen Bomb chemical explosion fission fusion fusion increases the fission rate more powerful than the atomic bomb
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F. Others Food Irradiation radiation is used to kill bacteria Radioactive Tracers explore chemical pathways trace water flow study plant growth, photosynthesis Consumer Products ionizing smoke detectors - 241 Am
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