Isotopes of silicon

Silicon (₁₄Si) has 25 known isotopes, with mass number ranging from 22 to 46. Si (the most abundant isotope, at 92.24%), Si (4.67%), and Si (3.07%) are stable. The longest-lived radioisotope is Si, which occurs naturally in tiny quantities from cosmic ray spallation of argon. Its half-life has been determined to be approximately 157 years; it beta decays with energy 0.21 MeV to P, which in turn beta-decays, with half-life 14.269 days to S; neither step has gamma emission. After Si, Si has the second longest half-life at 157.2 minutes. All others have half-lives under 7 seconds.