| Themes > Science > Physics > Nuclear Physics > ABC's of Nuclear Science > Radioactivity > Half-life |
The time required for half of the atoms in any given quantity of a radioactive isotope to decay is the half-life of that isotope. Each particular isotope has its own half-life. For example, the half-life of 238U is 4.5 billion years. That is, in 4.5 billion years, half of the 238U on Earth will have decayed into other elements. In another 4.5 billion years, half of the remaining 238U will have decayed. One fourth of the original material will remain on Earth after 9 billion years. The half-life of 14C is 5730 years, thus it is useful for dating archaeological material. Nuclear half-lives range from tiny fractions of a second to many, many times the age of the universe. |
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