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Radioactive Elements Part 1 Jan 2, 2013
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Radioactivity: An Imbalance of Forces in the Nucleus
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Forces dependent on distance SO.. Larger nuclei are less stable Neucleons less effective in holding nucleus together Electrical (repulsive) forces have greater impact
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Types of Radioactive Particles Alpha Particles – 2 protons and 2 neutrons Beta Particles – split 1 neutron into 1 proton and 1 electron Gamma Particles – emits a photon
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Half Life: Measures Decay Rate Half life refers to amount of time it takes for ½ of the radio active sample to decay Half life for a particular isotope is always the same
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Half Life Half life measures decay rate Ex. Every1620 years ½ of a sample of radium-226 will have decayed. Start 1620 years 3240 years 6480 years
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Radioactive Elements Part 2 Jan 4, 2013
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Half-life: Exponential Decay
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Decay of 238 U: Natural Decay Chain
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decays, through alpha-emission, with a half-life of 4.5 billion years to thorium-234 which decays, through beta-emission, with a half-life of 24 days to protactinium-234 which decays, through beta-emission, with a half-life of 1.2 minutes to uranium-234 which decays, through alpha-emission, with a half-life of 240 thousand years to thorium-230 which decays, through alpha-emission, with a half-life of 77 thousand years to radium- 226 which decays, through alpha-emission, with a half-life of 1.6 thousand years to radon- 222 which decays, through alpha-emission, with a half-life of 3.8 days to polonium-218 which decays, through alpha-emission, with a half-life of 3.1 minutes to lead-214 which decays, through beta-emission, with a half-life of 27 minutes to bismuth-214 which decays, through beta-emission, with a half-life of 20 minutes to polonium-214 which decays, through alpha-emission, with a half-life of 160 microseconds to lead-210 which decays, through beta-emission, with a half-life of 22 years to bismuth-210 which decays, through beta-emission, with a half-life of 5 days to polonium-210 which decays, through alpha-emission, with a half-life of 140 days to lead-206, which is a stable nuclide.
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Types of Radioactive Particles Alpha Particles – 2 protons and 2 neutrons Beta Particles – split 1 neutron into 1 proton and 1 electron Gamma Particles – emits a photon
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Types of Radioactive Particles Alpha Particles – 2 protons and 2 neutrons Lowest Energy Still fast enough to do damage Easily stopped Relatively large size and mass Large enough to do damage Easily stopped +2 Charge. Tends to pick up electrons & convert to Helium
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Types of Radioactive Particles Alpha Particles Emits: 2 p + 2 n Example: Uranium-238 Thorium-234 + Helium-4 ElementAtomic # (# protons) Mass # (# p + # n) # neutrons Uranium92238146 Thorium90234144 Helium242
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Types of Radioactive Particles Beta Particles - 1 n 1 p + 1 e - (emits e - ) Higher Energy Harder to stop than α particle Becomes part of material when stopped
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Types of Radioactive Particles Beta Particles Loses: 1 n Gains: 1 p Emits: 1 e - Example: Thorium -234 Protactinium – 234 + electron ElementAtomic # (# protons) Mass # (# p + # n) # neutrons Thornium90234144 Protactinium91234143
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Types of Radioactive Particles Gamma Particles – emits a photon Highest Energy Can do significant damage Hard to stop No charge Doesn’t combine with other materials No mass Hard to stop
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