Isotopes of tin

Tin (₅₀Sn) is the element with the greatest number of naturally abundant isotopes, 10. Seven, ^114-120Sn, are theoretically stable, while the remaining three, ¹¹²Sn, ¹²²Sn, and ¹²⁴Sn, are potentially radioactive to double beta decay, but have not been observed to decay. This is generally attributed to the fact that 50 is a "magic number" of protons. In addition, 32 unstable tin isotopes are known, including tin-100 (¹⁰⁰Sn) and tin-132 (¹³²Sn), which are both "doubly magic". The longest-lived of these is tin-126 (¹²⁶Sn), with a half-life about 230,000 years; with all others less than a year and the majority under 20 minutes.

The number of known metastable states is very large, including a long series of low-lying states in odd isotopes from 117 on, which gives two nuclides with a longer life than any ground-state radioisotope other than 126: ^121mSn, half-life 43.9 years, and ^119mSn, half-life 293.1 days.