Isotope persisted down to the present because their rate of decay is so slow (e.g. uranium-238 and potassium-40). Post-primordial isotopes were created by cosmic ray bombardment as cosmogenic nuclides (e.g., tritium, carbon-14), or by the decay of a radioactive primordial isotope to a radioactive radiogenic nuclide daughter (e.g. uranium to radium). A few isotopes are naturally synthesized as nucleogenic nuclides, by some other natural nuclear reaction, such as when neutrons from natural nuclear fission are absorbed by another atom. As discussed above, only 80 elements have any stable isotopes, and 26 of these have only one stable isotope. Thus, about two-thirds
Pertechnetate is found in a Meckel's diverticulum with Meckel's scans. All technetium salts are mildy radioactive, but some of them have explored use of the element for its chemical properties. In these uses, its radioactivity is incidental, and generally the least radioactive (longest-lived) isotopes of Tc are used. In particular, Tc (half-life 211,000 years) is used in corrosion research, because it is the decay product of the easily obtained commercial Tc isotope, which is its nuclear isomer. In theory, the longest-lived technetium isotope, Tc (half-life 4.2 million years), would be the optimal isotope for this use. Solutions of technetate(VII) react with