Post on 23-Jan-2016
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Radioactivity
Radioactivity The process by which nuclei emit particles
and rays These penetrating particles and rays are
called radiation.
Types of Radiation
Alpha particle-two p+ and two n0 (helium nucleus) Changes identity of the atom (drops by two atomic #’s) Little penetrating power (stopped by paper or skin)
Symbol is 2He or 2α4 4
Types of Radiation Beta particle- a high speed e-
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 Gamma Radiation
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 The symbols for the various particles are
shown:
When a radioisotope changes identity, this is called a transmutation reaction.
Half-Life
Every radioisotope has its own rate of decay measured by its half-life. 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 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.
Fission Chain Reaction In a chain reaction, the neutrons produced
strike other atoms, which produce more neutrons, etc. This is how a nuclear bomb works. It is also how reactors work, but with controls.
Nuclear Reactors Make use of the energy produced by fission.
Nuclear Reactors The fuel rods from reactors, when spent, are a
major waste issue. 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 Occurs when nuclei combine to produce a
heavier nucleus. Occurs naturally in the sun. (4 H nuclei become 1 He
nucleus) It is how current nuclear warheads work.