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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.
In contrast, the radioactive nuclide beryllium-7 falls into the same light element range but has a half-life too short for it to have been formed before the formation of the Solar System, so that it cannot be a primordial nuclide. Since the cosmic ray spallation route is the most likely source of beryllium-7 in the environment, that isotope is ...
Certain light (low atomic number) primordial nuclides (isotopes of lithium, beryllium and boron) are thought to have been created not only during the Big Bang, but also (and perhaps primarily) to have been made after the Big Bang, but before the condensation of the Solar System, by the process of cosmic ray spallation on interstellar gas and ...
It is prevented from having a stable isotope with 4 protons and 6 neutrons by the very large mismatch in proton/neutron ratio for such a light element. (Nevertheless, beryllium-10 has a half-life of 1.36 million years, which is too short to be primordial, but still indicates unusual stability for a light isotope with such an imbalance.)
Indeed, none of these primordial isotopes of the elements from beryllium to oxygen have yet been detected, although those of beryllium and boron may be able to be detected in the future. So far, the only stable nuclides known experimentally to have been made during Big Bang nucleosynthesis are protium, deuterium, helium-3, helium-4, and lithium-7.
Two beta-decay stable nuclides exist for odd neutron numbers 1 (2 H and 3 He), 3 (5 He and 6 Li – the former has an extremely short half-life), 5 (9 Be and 10 B), 7 (13 C and 14 N), 55 (97 Mo and 99 Ru), and 85 (145 Nd and 147 Sm); the first four cases involve very light nuclides where odd-odd nuclides are more stable than their surrounding ...
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.