Beryllium-10
Beryllium-10 (10Be) is a radioisotope of beryllium. It is formed in the Earth's atmosphere mainly by cosmic ray spallation of nitrogen and oxygen. Beryllium-10 has a half-life of 1.39 × 106 years. It decays by beta decay to boron-10. It has a maximum energy of 556.2 keV. It decays through the reaction 10Be→10B + e−.