Radionuclide
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A radionuclide is a nuclide that is unstable and known to undergo radioactive decay into a different nuclide, which may be another radionuclide or be stable. Radiation emitted by radionuclides is almo
Americium-241 emitting alpha particles inserted into a cloud chamber
Americium-241 container in a smoke detector
Americium-241 capsule as found in smoke detector. The circle of darker metal in the center is americium-241; the surrounding casing is aluminium.
Radioactive decay
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Radioactive decay is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay
Radionuclide
…A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that is unstable and known to undergo radioactive decay into a different nuclide, which may be another radionuclide (see decay chain) or be stable. Radiation emitted by radionuclides is almost always ionizing…
Pierre and Marie Curie in their Paris laboratory, before 1907
Taking an X-ray image with early Crookes tube apparatus in 1896. The Crookes tube is visible in the centre. The standing man is viewing his hand with a fluoroscope screen; this was a common way of setting up the tube. No precautions against radiation exposure are being taken; its hazards were not known at the time.