A primordial nuclide is a type of isotope that has existed since the formation of the Earth, which is approximately 4.5 billion years ago. These nuclides were formed during the early nucleosynthesis processes in the universe shortly after the Big Bang, as well as during and after stellar processes in ancient stars. Primordial nuclides include stable isotopes, like hydrogen (^1H), helium (^4He), and some other isotopes that are stable over long periods of time.
