Both stable and unstable isotopes of beryllium are created in stars, but the radioisotopes do not last long. It is believed that most of the stable beryllium in the universe was originally created in the interstellar medium when cosmic rays induced fission in heavier elements found in interstellar gas and dust. Primordial beryllium contains only one stable isotope, 9Be, and therefore beryllium is, uniquely among all stable elements with an even atomic number, a monoisotopic and mononuclidic element.
Both stable and unstable isotopes of beryllium are created in stars, but the radioisotopes do not last long. It is believed that most of the stable beryllium in the universe was originally created in the interstellar medium when cosmic rays induced fission in heavier elements found in interstellar gas and dust. Primordial beryllium contains only one stable isoto.pe, 9Be, and therefore beryllium is, uniquely among all stable elements with an even atomic number, a monoisotopic and mononuclidic element