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Radioactivity, Stability

radioactivity - tendency to decay, emit particles

  • radionuclides - radioactive nuclei
  • radioisotopes - atoms w/ radioactive nuclei
  • alpha radiation - emitting alpha particles (helium-4 nuclei)
    • atomic number decreases by 2
    • atomic mass decreases by 4
  • beta radiation - emits electrons from unstable nucleus
    • neutron >> proton
    • atomic number increases by 1
    • atomic mass stays the same
  • gamma radiation - emits high-energy photons
    • accompanies other radioactive emissions
    • doesn’t change atomic number/mass
  • electron capture - nucleus gains electron from surrounding electron cloud
    • proton >> neutron
    • atomic number decreases by 1
    • atomic mass stays the same

nuclear stability - depends on multiple factors

  • neutron-proton ratio - neutron # > proton # to ensure stability in atoms w/ large atomic numbers
    • belt of stability - area in which all stable nuclei are found
    • all nuclei w/ 84+ protons are radioactive
    • nuclei above belt of stability use beta emission >> increases proton #, decreases neutron #
    • nuclei below belt of stability use electron capture, positron emission >> decrease proton #, increase neutron #
    • nuclei with over 84 protons use alpha emission
  • radioactive series - aka nuclear disintegration series
    • 3 naturally occurring series end with lead
    • stability not achieved w/ a single emission (needs a series of emissions)
  • magic numbers - 2, 8, 20, 28, 50, 82 protons; 2, 8, 20, 28, 50, 82, 126 neutrons
    • usually more stable when w/ these numbers
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