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Radioactive decay
emission of subatomic particles by the decay of an atomic nucleus / From Wikipedia, the free encyclopedia
Radioactive decay happens to some chemical elements. Most chemical elements are stable. Stable elements are made up of atoms that stay the same. Even in a chemical reaction, the atoms themselves do not ever change.
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In the 19th century, Henri Becquerel discovered that some chemical elements have atoms that change over time. In 1898, Marie and Pierre Curie called this phenomenon radioactive decay.[1] Becquerel and the Curies were awarded the Nobel Prize in Physics for this discovery, in 1903.