4.4 Radioactivity - PowerPoint PPT Presentation

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4.4 Radioactivity

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4.4 Radioactivity Nuclear Reaction - involves change in nucleus Radioactivity substances spontaneously emit radiation. Element can change into another element. – PowerPoint PPT presentation

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Title: 4.4 Radioactivity


1
4.4 Radioactivity
2
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

3
Nuclear vs. Chemical Reactions
  • Nucleus is changed

Atoms are rearranged
4
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
5
Penetration of Radiation
6
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

7
Beta Emission Ex. Carbon-14 decays to produce a
beta particle.
  • 14C ? 14N 0ß
  • 6 7 -1
  • beta

8
Gamma Emission accounts for most of energy lost
during radioactive decay.
  • Usually accompanies alpha beta.
  • 238U ? 234Th 4He 0?
  • 92 90 2 0

9
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.

10
Radioactive Decay Series
11
Nuclear Fission (Splitting)
  • Unstable atoms break apart into smaller ones.
  • Releases tremendous amounts of energy.
  • Nuclear power plants (U-235)

12
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.

13
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.

14
Coal vs. Nuclear Power
15
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).

16
15 power by nuclear52 by coal power
17
The End
  • Chain Reaction Neutrons released start
  • new reactions
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