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Nuclear Chemistry

Nuclear Chemistry. Chapter 4.4 and 25. Particle Accelorators. Lawrence’s cyclotron: http://www.lbl.gov/Science-Articles/Archive/early-years.html FermiLab http://www.fnal.gov/ CERN http://public.web.cern.ch/public/ A.k.a. “Large hadron collider” (LHC)

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Nuclear Chemistry

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  1. Nuclear Chemistry Chapter 4.4 and 25

  2. Particle Accelorators • Lawrence’s cyclotron: http://www.lbl.gov/Science-Articles/Archive/early-years.html • FermiLabhttp://www.fnal.gov/ • CERN http://public.web.cern.ch/public/ • A.k.a. “Large hadron collider” (LHC) • SuperColliderhttp://www.hep.net/ssc/

  3. Chemical vs. Nuclear Reactions Chemical Nuclear • Bonds are broken or formed. • Atoms are unchanged, but rearranged. • Involve valence electrons. • Associated with small energy changes. • Reaction rate influenced by temp, pressure, concentration, catalysts. • Nuclei emit particles and/or rays. • Atoms are converted into atoms of another element. • Involve protons, neutrons, and electrons. • Associated with large energy changes. • Reaction rate not normally affected by temp, pressure, catalysts.

  4. Radioactivity • Radiation – the rays and particles emitted by the radioactive material • Radioactive atoms undergo significant changes in their identity • Atoms of one element change to atoms of another element • Reason? Nuclei are unstable • Gain stability by losing energy

  5. What types of radiation do nuclei emit? • Radioisotopes – isotopes of the same atoms with unstable nuclei • Undergo radioactive decay to become more stable • Most common radiation types: • Alpha • Beta • Gamma

  6. Nuclear Stability • Which atomic nuclei are radioactive? • Neutrons – add attractive force within the nucleus • Stability – related to balance between electrostatic and strong nuclear forces • Neutron/proton ratio • Low atomic numbers ~1:1 ratio • High atomic numbers ~1.5:1 ratio • Figure 25.8 p. 811

  7. Type of decay depends on reason for instability • Too many neutrons to be stable (above band of stability): • Beta decay • Alpha decay • Gamma decay • Too few neutrons to be stable (below band of stability): • Positron emission • Electron capture

  8. Types of Decay Notes on Board….

  9. Radioactive Decay Rates • Radioisotopes have differing decay rates • Half-life – time required for one-half of a radioisotope’s nuclei to decay into its products • Example: • Strontium-90 half-life (t) = 29 years • Today - 10.0 g strontium • 29 years from now – 5.0 g strontium

  10. Radioactive Decay Rates • Equation: amount remaining = initial amount (1/2)n OR amount remaining = initial amount (1/2)t/T t = time elapsed T = duration of one half life *** must have same units of time • Table 25.5 p. 818 • Radioisotopes all have different half-lives

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