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In a chemical reaction, the half-life of a species is the time it takes for the concentration of that substance to fall to half of its initial value. In a first-order reaction the half-life of the reactant is ln(2)/λ, where λ (also denoted as k) is the reaction rate constant.
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.
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 ...
Mercury (as methylmercury) in the body has a half-life of about 65 days. Lead in the blood has a half life of 28–36 days. [29] [30] Lead in bone has a biological half-life of about ten years. Cadmium in bone has a biological half-life of about 30 years. Plutonium in bone has a biological half-life of about 100 years.
It has a short half-life of about 7.1 s, [4] but its decay back to 16 O produces high-energy gamma radiation (5 to 7 MeV). [ 4 ] [ 10 ] Because of this, access to the primary coolant piping in a pressurised water reactor must be restricted during reactor power operation. [ 10 ]
Hg with a half-life of 444 years, and 203 Hg with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lives that are less than a day. 206 Hg occurs naturally in tiny traces as an intermediate decay product of 238 U. 199 Hg and 201 Hg are the most often studied NMR-active nuclei, having spins of 1 ⁄ 2 and 3 ⁄ 2 ...
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 ...
The most stable isotope of the element is promethium-145, which has a specific activity of 139 Ci/g (5.1 TBq/g) and a half-life of 17.7 years via electron capture. [ 4 ] [ 22 ] Because it has 84 neutrons (two more than 82, which is a magic number which corresponds to a stable neutron configuration), it may emit an alpha particle (which has 2 ...