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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 decay series of uranium-235 (historically called actino ...
All isotopes from 232 U to 236 U inclusive have minor cluster decay branches (less than 10 −10 %), and all these bar 233 U, in addition to 238 U, have minor spontaneous fission branches; [7] the greatest branching ratio for spontaneous fission is about 5 × 10 −5 % for 238 U, or about one in every two million decays. [118]
Hence, a parent isotope is one that undergoes decay to form a daughter isotope. For example element 92, uranium, has an isotope with 144 neutrons (236 U) and it decays into an isotope of element 90, thorium, with 142 neutrons (232 Th). The daughter isotope may be stable or it may itself decay to form another daughter isotope.
The other two types of decay are observed in all the elements. Lead, atomic number 82, is the heaviest element to have any isotopes stable (to the limit of measurement) to radioactive decay. Radioactive decay is seen in all isotopes of all elements of atomic number 83 or greater.
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.
All uranium isotopes present in natural uranium are radioactive and fissionable, and 235 U is fissile (will support a neutron-mediated chain reaction). Uranium, thorium, and one radioactive isotope of potassium (40 K) as well as their decay products are the main elements contributing to natural terrestrial radioactivity. [3]
Uranium-235 (235 U 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.
238 U abundance and its decay to daughter isotopes comprises multiple uranium dating techniques and is one of the most common radioactive isotopes used in radiometric dating. The most common dating method is uranium-lead dating , which is used to date rocks older than 1 million years old and has provided ages for the oldest rocks on Earth at 4. ...