4.4%20Radioactivity

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4.4 Radioactivity
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Nuclear Reaction - involves change in nucleus

• Radioactivity substances spontaneously emit
  radiation.
• Element can change into another element.
• Occurs because nucleus becomes unstable.
• Unstable atoms gain stability by losing energy.
• Energy lost by emitting radiation.
• Chemical Reaction change of 1 or more substances
  into new substances.
• atoms are rearranged
• nucleus is unchanged

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Nuclear vs. Chemical Reactions

• Nucleus is changed

Atoms are rearranged
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Types of Radiation
Type Symbol Mass Charge Nature Penetra- tion
Alpha 4 2He 4 2 Helium Nucleus Sheet of Paper
Beta ß 0 -1e 0 1/1840 -1 From nucleus High speed electrons Aluminum Foil
Gamma 0 0? 0 0 Electro- Magnetic Radiation Lead Shielding
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Penetration of Radiation
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Nuclear Equations Mass numbers atomic numbers
must be conserved.

• Alpha emission
• 226Ra ? 222Rn 4He
• 88 86 2
• alpha particle
• Mass and Atomic Conserved
• 226 ? 222 4
• 88 ? 86 2

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Beta Emission Ex. Carbon-14 decays to produce a
beta particle.

• 14C ? 14N 0ß
• 6 7 -1
• beta

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Gamma Emission accounts for most of energy lost
during radioactive decay.

• Usually accompanies alpha beta.
• 238U ? 234Th 4He 0?
• 92 90 2 0

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Nuclear stability primarily determined by

• Ratio of neutrons to protons.
• Size of nucleus.
• Atoms with atomic greater than 83 (Bismuth) are
  unstable.
• Atoms eventually decay to form stable,
  nonradioactive atoms.

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Radioactive Decay Series
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Nuclear Fission (Splitting)

• Unstable atoms break apart into smaller ones.
• Releases tremendous amounts of energy.
• Nuclear power plants (U-235)

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Nuclear Fusion (Uniting)

• Fusing together smaller elements to make larger
  ones.
• Produces all elements larger than He
• Fusion releases tremendous amounts
  of energy. (Greater than fission)
• Occurs on the Sun (and stars)
• Cleaner method but no current
  technology for power plants.

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Nuclear Energy (Fission)Pros Cons

• Does not cause air pollution
• (no CO2 emissions, etc.)
• Doesnt use up
• fossil fuel (coal)
• Less global warming, acid rain

• Limited amount of nuclear fuel (Ex. U-235)
• Spent fuel is radioactive
• Transportation storage problems!
• Water used in cooling process may cause problems
  when released to environment.

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Coal vs. Nuclear Power
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Pro Con

• Coal waste has more radiation than spent fuel!
• Except for Chernobyl, minimal releases of
  radiation.

• High cost of nuclear power (due to government
  regulations).

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15 power by nuclear52 by coal power
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The End

• Chain Reaction Neutrons released start
• new reactions