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.