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A similar radiogenic series is derived from the long-lived radioactive primordial nuclide 232 Th. These nuclides are described as geogenic, meaning that they are decay or fission products of uranium or other actinides in subsurface rocks. [6] All such nuclides have shorter half-lives than their parent radioactive primordial nuclides.
One of the primordial nuclides is tantalum-180m, which is predicted to have a half-life in excess of 10 15 years, but has never been observed to decay. The even-longer half-life of 2.2 × 10 24 years of tellurium-128 was measured by a unique method of detecting its radiogenic daughter xenon-128 and is the longest known experimentally measured ...
The Solar System and Earth are formed from primordial nuclides and extinct nuclides. Extinct nuclides have decayed away, but primordial nuclides still exist in their original state (undecayed). There are 251 stable primordial nuclides, and remainders of 35 primordial radionuclides that have very long half-lives.
They occur in the decay chains of primordial isotopes of uranium or thorium. Some of these nuclides are very short-lived, such as isotopes of francium. There exist about 51 of these daughter nuclides that have half-lives too short to be primordial, and which exist in nature solely due to decay from longer lived radioactive primordial nuclides.
The next group is the primordial radioactive nuclides. These have been measured to be radioactive, or decay products have been identified in natural samples (tellurium-128, barium-130). There are 35 of these (see these nuclides ), of which 25 have half-lives longer than 10 13 years.
By convention, certain stable nuclides of lithium, beryllium, and boron are thought to have been produced by cosmic ray spallation in the period of time between the Big Bang and the Solar System's formation (thus making these primordial nuclides, by definition) are not termed "cosmogenic", even though they were formed by the same process as the ...
A chart or table of nuclides maps the nuclear, or radioactive, behavior of nuclides, as it distinguishes the isotopes of an element.It contrasts with a periodic table, which only maps their chemical behavior, since isotopes (nuclides that are variants of the same element) do not differ chemically to any significant degree, with the exception of hydrogen.
In contrast, all even neutron numbers from 6 to 124, except 84 and 86, have at least two observationally stable nuclides. Neutron numbers for which there is a stable nuclide and a primordial radionuclide are 27 (50 V), 65 (113 Cd), 81 (138 La), 84 (144 Nd), 85 (147 Sm), 86 (148 Sm), 105 (176 Lu), and 126 (209 Bi).