Radioactive Decay

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Radioactive Decay
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Radioactivity

• Nucleus of element spontaneously
• emits subatomic particles
• electromagnetic waves
• Nucleus changes into different element
• when this happens
• Original nucleus is unstable
• Process called radioactive decay or
  transmutation

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Characteristics of RadiationSee Table O
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4
2 Neutrons 2 Protons Charge 2 Mass 4amu
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Beta Particle fast moving electron
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Can we predict exactly when an atom will decay?

• NO!
• For large s of atoms, we CAN predict how many
  will decay on average in a given amount of time

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Whats Going on in the Nucleus?

• repulsions between protons so want to fly apart
  but...
• protons neutrons attracted to each other by
  nuclear strong force so...
• neutrons help hold nucleus together

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Strong Force

• Works best if nucleus isnt too large
• As size nucleus ?, need more neutrons to
  counteract repulsions between protons
• Eventually, nucleus too large to be stable

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Balancing Act

• Balance exists between repulsive force nuclear
  strong force

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Beyond Element 83

• No amount neutrons can hold nucleus together once
  it has 83 protons
• All Elements 83 and above on PT
• are radioactive
• Other elements may have radioactive isotopes
• 
  applet

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Natural Radioactivity Unstable Nuclei Emit
Radiation

• Spontaneous nuclear change
• Forms new kind of atom
• Type of decay mode named for particle emitted
  (see table N)

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Nuclear Equations

• Describe decay process
• reactants (starting side left) ? products
  (ending side right)
• ? separates two sides
• ( yields)