|
Sciencetime© 2010
reproduction by permission
of author
| |
| Most naturally occurring radioactive
materials and many fission products; undergo radioactive decay
through a series of transformations rather than in a single step.
Until the last step, these radionuclides emit energy or particle
with each transformation and become another radionuclide. Man-made
elements, which are all heavier than uranium and unstable, undergo
decay in this way. This decay chain, or decay series, ends in a
stable nuclide.
For example:
Uranium-238 decays through a
series of steps to become a stable form of lead. Each step in the
illustration below, indicates a different nuclide. Only a few of the
steps are labeled, and the numbers below each label indicate the
length of the particular radionuclide's half-life. Uranium-238 has
the longest half-life, 4.5 billion years, and radon-222 the
shortest, 3.8 days. The last radionuclide in the chain, polonium-210
transforms to lead-210, a stable nuclide.
Uranium-238 Decay Chain
|
|
|
|