Transcript Radioactivity Notes

Radioactivity
Radioactivity
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The process by which nuclei emit particles
and rays
These penetrating particles and rays are
called radiation.
Types of Radiation
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Alpha particle-two p+ and two n0 (helium nucleus)
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Changes identity of the atom (drops by two atomic #’s)
Little penetrating power (stopped by paper or skin)
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Symbol is 42He or 42α
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Types of Radiation
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Beta particle- a high speed e
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Comes from a neutron that breaks apart
Changes identity of the atom (up one atomic #)
Stopped by Al foil or wood
Symbol is -1e or -1β
Types of Radiation
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Gamma Radiation
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High-energy photon emitted as a gamma ray
Often emitted along with α or β radiation
Does not change identity of the isotope
Highly penetrating and very dangerous to
humans
Radioactive Decay as Equations
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The symbols for the various particles are
shown:
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When a radioisotope changes identity, this
is called a transmutation reaction.
Half-Life
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Every radioisotope has its own rate of decay
measured by its half-life.
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Half-life (t½) is the time required for half the nuclei of
that radioisotope to decay
Could be a fraction of a second or billions of years.
Fission
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When nuclei of some isotopes are hit with
neutrons, they split into smaller fragments. This
is fission.
Every time an isotope splits, TREMENDOUS
amounts of energy are released.
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Fission Chain Reaction
In a chain reaction, the neutrons produced
strike other atoms, which produce more
neutrons, etc.
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This is how a nuclear bomb works.
It is also how reactors work, but with controls.
Nuclear Reactors
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Make use of the energy produced by fission.
Nuclear Reactors
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The fuel rods from reactors, when spent, are a
major waste issue.
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They are stored indefinitely, or shipped to another
location.
They won’t be safe until the isotopes are stable,
which depends on the half-life of the isotope.
The next slide has some fuel rod photos.
Fuel Rods
Fusion
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Occurs when nuclei combine to produce a
heavier nucleus.
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Occurs naturally in the sun. (4 H nuclei become 1 He
nucleus)
It is how current nuclear warheads work.