The phenomenon of radioactivity was first reported in 1896 by Henri Becquerel for a uranium salt. In 1898, Marie Curie and her husband Pierre Curie discovered two other radioactive elements–radium and polonium.

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During radioactive decay, the radioactive element may emit positively charged alpha particles, negatively charged beta particles, gamma rays or X-rays.

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Alpha particles are the least penetrating type of radiation. Even the most energetic alpha particles can be stopped by a single sheet of paper.

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Radiocarbon dating, or carbon-14 dating, is a scientific method that can accurately determine the age of organic materials as old as approximately 60,000 years.

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Chernobyl was the worst nuclear disaster in history, releasing more than 400 times as much radioactive material as the Hiroshima atomic bomb. An uncontrollable chain reaction inside the reactor caused a sharp increase in temperature that ultimately resulted in the fusion of the fuel rods, a steam explosion and a fire.

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