Nuclear Radiation Notes

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Nuclear Radiation Notes
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Nuclear Radiation Notes

• Nuclei are unstable when they have low amounts of
  binding energy.
• When they are unstable, they are more likely to
  break into pieces.

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Nuclear Radiation Notes

• Nuclear reactions happen when a change occurs in
  the nucleus.
• Nuclear Fission is when the nucleus breaks apart
  in some way
• Nuclear Fusion is when particles combine in some
  way

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Nuclear Radiation Notes

• There are many different types of radiation
• 1. Alpha particle emission--a nucleus could lose
  an alpha particle, which is essentially the same
  thing as the nucleus of a helium atom. An alpha
  particle has two protons and two neutrons, but no
  electrons (so it has a 2 charge). This is a
  type of fission.

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Nuclear Radiation Notes

• A nucleus will tend to undergo alpha particle
  emission if it is too heavy or it has a low
  neutron-proton ratio. After alpha particle
  emission, the resulting nucleus will have a
  higher N/P ratio, and will be smaller.

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Nuclear Radiation Notes

• 2. Beta particle emission--a beta particle is
  just like a high speed electron. It has
  relatively no mass, and has a charge of -1. A
  nucleus will undergo beta particle emission if it
  has too high of a N/P ratio, and therefore the
  resulting nucleus will have a lower ratio. This
  is also a type of fission.

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• Wait! How can an electron come out of a nucleus,
  which only contains protons and neutrons?

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Nuclear Radiation Notes

• This is what you can visualize in your head for
  how the electron can be emitted from a neutron.
• See what happens to the neutron after the
  electron (beta-part.) leaves

http//niels.christoffersen.person.emu.dk/natpr/fy
sanimat/beta.htm
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Nuclear Radiation Notes

• 3. Gamma ray emission--a gamma ray is a
  high-energy (high frequency/short wavelength)
  light wave.
• It has no mass and no charge, and only is emitted
  at the same time as either alpha or beta
  particles.
• This is a type of fission

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Nuclear Radiation Notes

• Other less common forms of radiation
• 4. Positron emission--A positron is essentially
  the opposite of an electron. It has relatively
  no mass, but has a charge of 1. Also a type of
  fission.

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Nuclear Radiation Notes

• When a positron leaves a nucleus, what is
  happening is that a proton is losing its charge,
  and therefore turns into a neutron. Positrons
  will be released from a nucleus if the N/P ratio
  is too low.

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Nuclear Radiation Notes

• 5. Electron Capture--this is a process where an
  electron loses its energy that keeps it in an
  energy level, and gets pulled into the nucleus.
  This is a type of fusion.

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Nuclear Radiation Notes

• When this happens, the negative charge of the
  electron cancels out the positive charge of a
  proton, and the proton is turned into a neutron.
  
• This has the same effect upon the nucleus as
  Positron Emission (raises the N/P ratio).

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Nuclear Radiation Notes

• How do we describe these radioactive occurrences
  using equations?
• First we need to be able to describe nuclei
• Uranium with an atomic number of 92 and a
  atomic weight of 238

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Nuclear Radiation Notes

• Therefore, an alpha particle is
• or

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Nuclear Radiation Notes

• A Beta particle can be described as
• A gamma ray is written simply as
• A positron is written as

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Nuclear Radiation Notes

• A nuclear equation has a direction
• The arrow signifies which particles existed
  before the change (reactants) and which ones were
  present after the change occurred (products)

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Nuclear Radiation Notes

• In a nuclear reaction, the identity of the
  elements can change, but the total mass and
  amount of charge must stay the same. To ensure
  that our equation shows this, we must balance the
  equation
• Try example on page 869.

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Nuclear Radiation Notes

• Any single naturally-occurring nuclear reaction
  will have a specific rate that it happens.
• This rate is measured with a half-life, which
  is the amount of time that it would take for half
  of a sample of radioactive material to decay
  naturally.
• The time it would require for a half-life to
  elapse can be calculated with the following
  equation N No(1/2)n (see pg. 871)

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Nuclear Radiation Notes

• Although radioactive decay (nuclear fission)
  happens naturally to unstable nuclei, it can also
  be done artificially (in labs).

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Nuclear Radiation Notes

• This is called nuclear bombardment, when a
  particle is put in a collision with another
  particle, encouraging one or both of them to
  break apart or stick together.

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Nuclear Radiation Notes

• Oftentimes a nuclear fission reaction will cause
  a chain reaction with many final products being
  generated by many separate fission reactions

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Nuclear Radiation Notes

• This is how most controlled (power plants)
  fission reactions occur
• as well as uncontrolled fission reactions
  (nuclear explosions)

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Nuclear Radiation Notes

• The opposite of nuclear fission is nuclear
  fusion. This is the process where two particles
  combine to form one nucleus. This will only
  occur if there is enough energy (heat) and is
  common on the sun, for instance.

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Nuclear Stability Notes
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Nuclear Radiation Notes

• Most scientists believe that all known elements
  have arisen from some type of nuclear fusion
  (mostly in stars).

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Nuclear Radiation Notes

• Every element above Uranium (92) has been
  created by humans using some type of nuclear
  fusion through bombardment (see pg. 625).