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Nuclear Chemistry. 1. Brief History of Radioactivity. 1896: Henri Becquerel of France discovers radioactivity; considered father of radioactivity 1896: Marie Curie discovered the radioactive elements Radium and polonium; came up with the term radioactivity
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1. Brief History of Radioactivity • 1896: Henri Becquerel of France discovers radioactivity; considered father of radioactivity • 1896: Marie Curie discovered the radioactive elements Radium and polonium; came up with the term radioactivity • 1911: Ernest Rutherford, was the first to discover the nucleus and first to artificially transmutate an element.
2. Radiation Exposure Background radiation is the nuclear radiation that arises naturally from cosmic rays and from radioactive isotopes in the soil and air. Radiation is measured in units of rems.
http://epa.gov/radtown/enter-radtown.html • http://www.hhs.iup.edu/sa/online/main/radhe2/radhemod1.htm ex of radiation sources • http://www.teachersdomain.org/asset/phy03_vid_everyday/ • http://www.ans.org/pi/resources/dosechart/
3. Benefits of Nuclear Radiation Smoke detectors use small alpha-emitting isotopes to detect smoke particles in the air. Radioactive tracers are used by medical professionals to detect biological abnormalities. Nuclear radiation therapy is used to treat cancer and other medical conditions. Radioactive tracers and radio-isotopes are used by scientists in understanding biochemical processes in plants. Source of electrical energy Irradiation of food products (kills bacteria)
4. Negative Aspects of Radiation Nuclear radiation can ionize atoms which causes a change in the number of electrons in an atom or molecule. These ionized particles then react differently from neutral particles. Radiation exposure has been linked to many types of cancer and can affect DNA which can result in mutations. Can cause burns. Can affect immunity, liver functions, muscle mass. Can cause death.
5. Precautions Taken To Limit Exposure People working in radioactive areas wear a dosimeter that measures the amount of radiation exposure. Use of protective shields when having X-rays. Radon tests to determine levels of radon found in the home due to radon that seeps in from the soil.
6. Fission Reaction 235 U + 1n -- 3 (1n) + 93Kr + 140Ba + Energy In this example, a slow moving neutron strikes an atom of U-235. It absorbs the neutron and becomes an unstable atom of U-236. It then undergoes fission. More neutrons are released in the reaction. These neutrons can strike other U-235 atoms to initiate their fission. Also a very small amount of mass is converted to a large amount of energy.
7. Nuclear Power - Fission Advantages Replaces fossil fuels (which are becoming scarcer) as a source of energy Does not produce gaseous pollutants • Disadvantages • Radioactive products of fission must be handled carefully • Storage of nuclear waste can be hard to find and expensive • Nuclear reactors are expensive to build
8. Nuclear Reactors A nuclear chain reaction is a continuous series of nuclear fission reactions. Controlled chain reactions are needed in order for a nuclear power plant to produce the right amount of steam to run the generators that ultimately produce electricity. The chain reaction starts with released neutrons that bombard the fissionable reactant (contained in fuel rods). The critical mass is the minimum mass of a fissionable isotope that provides the number of neutrons needed to sustain a chain reaction.
Chain reactions • http://www.kscience.co.uk/animations/chain_reaction.htm • http://www.visionlearning.com/library/flash_viewer.php?oid=3602 controlled vs uncontrolled • How nuclear energy works – YouTube • Fission And Fusion - YouTube
9. Regulation of fission process: • Moderators: Slow down the neutrons; slower moving neutrons are more likely to collide with other nuclei and thus cause a reaction • Control Rods: prevent neutrons from reaching other nuclei; prevents uncontrollable chain reaction • Coolants: carry away excess heat generated by the nuclear reaction Nuclear Reactor - YouTube
10. FUSION • Fusion reactions do not occur naturally on our planet but are the principal type of reaction found in stars • The large masses, densities, and high temperatures of stars provide the initial energies needed to fuel fusion reactions • The sun fuses hydrogen atoms to produce helium, • Ex: 11H + 31H → 42He + energy
11. Nuclear Power - Fusion Advantages: • Almost unlimited supply of hydrogen as the reactant • Produces extremely large amounts of energy Disadvantages: • Nuclear fusion reactions are difficult to produce in the laboratory • Requires extreme temperatures • Produces dangerous by-products
Study guides • http://www.bcscience.com/studybuzz/BCSci10-2008-Worksheet-06.pdf practice problems
worksheets • http://www.sciencegeek.net/Chemistry/chempdfs/nucleardecay.pdf • http://phet.colorado.edu/simulations/sims.php?sim=Radioactive_Dating_Game • http://www.csun.edu/~jte35633/worksheets/Chemistry/4-4NuclearEquations.pdf • http://www.chemteam.info/Radioactivity/WS-Radioactivity1.html
http://ab.mec.edu/abrhs/science/baumritter/#nuclearchemistryanchorhttp://ab.mec.edu/abrhs/science/baumritter/#nuclearchemistryanchor
Nuclear Chemistry Links • Nuclear chemistry presentation
Nuclear Chemistry • Radioactive decay • Radioactivity Online – Welcome • Balancing Nuclear Equations • FRONTLINE: nuclear reaction: fission and reprocessing
