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This picture shows radioactive decay of a carbon-14 atom. The carbon atom gives off a beta particle of radiation. The carbon atom turns into a nitrogen atom.
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Original artwork by Windows to the Universe staff (Randy Russell).

Radioactive Decay

Some materials are radioactive. They emit radiation. When an atom of a radioactive substance gives off radiation, it becomes a new type of atom. This process is called radioactive decay.

There are two main types of radiation that can be given off during radioactive decay. The first is particle radiation. It includes alpha and beta particles as well as proton and neutron radiation. The second is electromagnetic radiation. It includes high energy gamma rays and X-rays.

Most elements come in various "versions", called isotopes. Different isotopes have different numbers of neutrons. Some isotopes are radioactive. For example, the isotope of carbon called carbon-14 is radioactive. It has 8 neutrons (instead of the usual 6) and radiates beta particles. When an atom emits radiation it undergoes radioactive decay. It may be transformed from one isotope to another. It might become a different element altogether. When carbon-14 decays by emitting a beta particle, it becomes nitrogen-14. Isotopes that do not decay are called "stable" isotopes.

Different radioactive materials take different amounts of time to decay. Scientists use the idea of a half-life to describe this. The half-life of a radioactive material can be very short (less than a second) or very long (thousands of years) or anywhere in between. After one half-life, half of a sample of radioactive material has decayed. After another half-life, half of what was left decays.

Last modified August 26, 2009 by Randy Russell.

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