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 give off radiation. When an atom of a radioactive substance gives off radiation, it becomes a new type of atom. This change 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 different "versions", called isotopes. Some isotopes are radioactive. Carbon-14 is a radioactive isotope of carbon. Carbon-14 decays by emitting a beta particle. It becomes nitrogen-14, a different element! Some isotopes do not decay. They 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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