1.2 Stable and unstable nuclei

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  • Created by: maddie
  • Created on: 29-11-12 09:03
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  • Stable and unstable nuclei
    • Stable nucei don't disintergrate so must be force holding them together -strong nuclear force overc oming electrostatic force of replusion between protons
      • Range about 3-4 fm (10^-15).
      • atractive from from 4 - 0.5 fm then a repulsive force acting to prevent protons and neutrons being pushed together
    • Alpha radiation
      • alpha particle - two protons and two neutrons
      • proton number 2, mass number 4
    • Beta radiation
      • beta particle - fast moving electron
      • Negative charge, mass number 0
    • Gamma radiation
      • electromagnetic radiation emmited by unstable nucleus
      • Mass 0, charge 0
      • emitted by nucleus with too much energy after beta or alpha emission
      • can pass through metal
    • Neutron in nucleus of unstable atom turns into proton
      • beta particle produced and instantly emitted
        • antipartcle with no charge, antineutrino emitted
          • neutron -> proton, mass number stays same, proton number: +1
      • happens to nuclei with too many neutrons
    • when energy spectrum of beta particle first measured found they were released with kinetic energies up to max depending on isotope
      • Scientists puzzled - why energy of beta particle varuied to max when each unstable nuclei lost certain amount of energy in process.
        • Either energy not conerved or some take away in mysterious particles - neutrinos or antineutrinos
          • 20 years later antineutrino detected

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