Nuclear Chemistry

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Nuclear Chemistry
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Radioactivity

• One of the pieces of evidence for the fact that
  atoms are made of smaller particles came from the
  work of Marie Curie (1876-1934).
• She discovered radioactivity or radioactive
  decay, the spontaneous disintegration of the
  nuclei of some elements.

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Radioactivity or Radioactive Decay

• The property in which an unstable nucleus gives
  off particles and/or energy
• This changes the atomic number (p) and forms a
  new element

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Radiation

• The penetrating rays (energy or particles)
  emitted by a radioactive source

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Radioisotopes

• Unstable isotopes that undergo radioactive decay
• Elements with atomic number 83 and up are
  radioactive
• Bismuth and beyond..

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Nuclear Reactions vs. Normal Chemical Changes

• Normal Chemical Reactions involve rearranging
  atoms. The elements dont change.
• Nuclear reactions involve the nucleus
• The nucleus opens, and protons and neutrons are
  rearranged
• The opening of the nucleus releases a tremendous
  amount of energy that holds the nucleus together
  called binding energy

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Mass Defect

• Some of the mass can be converted into energy
• Shown by a very famous equation!
• Emc2

Energy Mass Speed of light
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Types of Radiation

• Alpha (a) a positively charged helium nucleus
• Beta (ß) an electron
• Gamma (?) pure energy called a ray rather than
  a particle

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Other Nuclear Particles

• Neutron
• Positron a positive electron
• Proton usually referred to as hydrogen-1
• Any other elemental isotope

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Penetrating Ability
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Balancing Nuclear Reactions

• In the reactants (starting materials on the
  left side of an equation) and products (final
  products on the right side of an equation)
• Atomic numbers must balance
• and
• Mass numbers must balance
• Use a particle or isotope to fill in the missing
  protons and neutrons

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Nuclear Reactions

• Alpha emission

Note that mass number (A) goes down by 4 and
atomic number (Z) goes down by 2.
Nucleons (nuclear particles protons and
neutrons) are rearranged but conserved
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Nuclear Reactions

• Alpha emission
• Try this one
• Po 210 undergoes alpha radiation

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Nuclear Reactions

• Beta emission

Note that mass number is unchanged and atomic
number goes up by 1.
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Nuclear Reactions

• Beta emission
• Try this one
• Uranium 238 undergoes beta decay

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Nuclear Fission
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Nuclear Fusion
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Nuclear Reaction
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Nuclear Power Plants
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So you say you want to meltdown your own power
plant? Heres your chance to play Homer Simpson.
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Nuclear Power Pros and Cons

• Lots of energy
• No green house gases
• Uses very little fuel

• Very small chance of massive disaster
• Potential target for terrorists
• Nuclear waste

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Accidents can happen

• The worst nuclear accident in US history occurred
  on Three Mile Island in PA 1979
• The reactor meltdown was caused by several
  mechanical errors as well as human error creating
  a coolant leak
• The reactor that had the melt down is no longer
  in use. The other reactor is slated to remain in
  use until 2034
• London Calling by The Clash is about this
  accident

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Chernobyl April 1986

• Chernobyl Nuclear Power Plant Pripyat, Ukraine
  April 1986
• During a test, the reactor received a power
  spike, causing several explosions
• Radiation was picked up several hundred miles
  away, prompting the Soviet Union to admit the
  accident, 3 days after it happened

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Japan Fukushima Power Plant March 2011
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Radiation Detection

• Film Badges exposure of film measures radiation
  exposure
• Geiger Counters- detect radiation through
  electric pulses in ionized gas
• Scintillation Counters- measure radiation from
  substances that emit visible light when energy is
  absorbed

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Radiation Detection
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Uses of Radiation

• Radioactive dating can determine the approximate
  age of an object
• There are many uses of radiation in the medical
  field
• Detect and kill cancerous cells
• X-Rays
• Many others
• Disinfect foods

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Personal Dose Chart
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Effects of Radiation on the Body
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Half Life

• Time it takes for ½ a sample to decay
• No two radioisotopes decay at the same rate
• Can be as short as a few seconds or take billions
  of years.

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Half Life

• Uranium-238 has a half-life of 4.5 billion years.
  Its stable ending element is lead (Pb)

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Half Life
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Half Life
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Half Life

• A 2.5 g sample of an isotope of strontium-90 was
  formed in a 1960 explosion of an atomic bomb at
  Johnson Island in the Pacific Test Site. The
  half-life of Sr-90 is 28 years.
• How many years will it take for 0.625 grams of
  Sr-90 to remain?
• What year will this be?

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Half Life

• A 2.5 g sample of an isotope of strontium-90 was
  formed in a 1960 explosion of an atomic bomb at
  Johnson Island in the Pacific Test Site. The
  half-life of Sr-90 is 28 years.
• How many years will it take for 0.625 grams of
  Sr-90 to remain? 56 years
• What year will this be? 2016

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Half Life

• The half-life of an isotope is 3.0 years. If 20
  mg of this isotope disintigrates over a period of
  12 years, how many mg of this isotope will remain?

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Half Life

• The half-life of an isotope is 3.0 years. If 20
  mg of this isotope disintigrates over a period of
  12 years, how many mg of this isotope will
  remain?
• 2.5 mg