Isotopes of silicon
has 23 known isotopes, with mass numbers ranging from 22 to 44. 28Si, 29Si, and 30Si are stable. The longest-lived radioisotope is 32Si, which is produced by cosmic ray spallation of argon. Its half-life has been determined to be approximately 150 years, and it decays by beta emission to 32P and then to 32S. After 32Si, 31Si has the second longest half-life at 157.3 minutes. All others have half-lives under 7 seconds.
