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Radioactive isotope table "lists ALL radioactive nuclei with a half-life greater than 1000 years", incorporated in the list above. The NUBASE2020 evaluation of nuclear physics properties F.G. Kondev et al. 2021 Chinese Phys. C 45 030001. The PDF of this article lists the half-lives of all known radioactives nuclides.
In this situation it is generally uncommon to talk about half-life in the first place, but sometimes people will describe the decay in terms of its "first half-life", "second half-life", etc., where the first half-life is defined as the time required for decay from the initial value to 50%, the second half-life is from 50% to 25%, and so on.
or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exists in nature as a primordial nuclide. Uranium-235 has a half-life of 703.8 million years.
All three isotopes are radioactive (i.e., they are radioisotopes), and the most abundant and stable is uranium-238, with a half-life of 4.4683 × 10 9 years (about the age of the Earth). Uranium-238 is an alpha emitter, decaying through the 18-member uranium series into lead-206.
The most stable of californium's twenty known isotopes is californium-251, with a half-life of 898 years. This short half-life means the element is not found in significant quantities in the Earth's crust. [a] 252 Cf, with a half-life of about 2.645 years, is the most common isotope used and is produced at Oak Ridge National Laboratory (ORNL ...
Tritium (from Ancient Greek τρίτος (trítos) ' third ') or hydrogen-3 (symbol T or 3 H) is a rare and radioactive isotope of hydrogen with a half-life of ~12.3 years. The tritium nucleus (t, sometimes called a triton) contains one proton and two neutrons, whereas the nucleus of the common isotope hydrogen-1 (protium) contains one proton and no neutrons, and that of non-radioactive ...
226 Ra is the most stable isotope of radium and is the last isotope in the (4 n + 2) decay chain of uranium-238 with a half-life of over a millennium; it makes up almost all of natural radium. Its immediate decay product is the dense radioactive noble gas radon (specifically the isotope 222 Rn ), which is responsible for much of the danger of ...
Eighteen isotopes and four nuclear isomers are known for einsteinium, with mass numbers 240–257. [2] All are radioactive; the most stable one, 252 Es, has half-life 471.7 days. [44] The next most stable isotopes are 254 Es (half-life 275.7 days), [45] 255 Es (39.8 days), and 253 Es (20.47 days). All the other isotopes have half-lives shorter ...