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Additionally, about 31 nuclides of the naturally occurring elements have unstable isotopes with a half-life larger than the age of the Solar System (~10 9 years or more). [ b ] An additional four nuclides have half-lives longer than 100 million years, which is far less than the age of the Solar System, but long enough for some of them to have ...
This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds. [1]
Only four of these 35 nuclides have half-lives shorter than, or equal to, the age of the universe. Most of the other 30 have half-lives much longer. The shortest-lived primordial, 235 U, has a half-life of 703.8 million years, about 1/6 the age of the Earth and Solar System.
They have shorter half-lives than primordial radionuclides. They arise in the decay chain of the primordial isotopes thorium-232, uranium-238, and uranium-235. Examples include the natural isotopes of polonium and radium. Cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to ...
This is because most of the universe's lithium, beryllium, and boron are made by cosmic ray spallation, not ordinary stellar nucleosynthesis, and beryllium has only one stable isotope (even that is a Borromean nucleus near the boundary of stability), causing it to lag in abundance with regard to its neighbors, each of which has two stable isotopes.
Unstable isotopes decay to their daughter products (which may sometimes be even more unstable) at a given rate; eventually, often after a series of decays, a stable isotope is reached: there are 251 stable isotopes in the universe.
In nuclear physics, the island of stability is a predicted set of isotopes of superheavy elements that may have considerably longer half-lives than known isotopes of these elements. It is predicted to appear as an "island" in the chart of nuclides , separated from known stable and long-lived primordial radionuclides .
Most stable isotopes on Earth are believed to have been formed in processes of nucleosynthesis, either in the Big Bang, or in generations of stars that preceded the formation of the Solar System. However, some stable isotopes also show abundance variations in the earth as a result of decay from long-lived radioactive nuclides.