There are seven stable isotopes of mercury (₈₀Hg) with ²⁰²Hg being the most abundant (29.74%). The longest-lived radioisotopes are ¹⁹⁴Hg with a half-life of 447 years, and ²⁰³Hg with a half-life of 46.61 days. Most of the remaining 40 radioisotopes have half-lives that are less than a day. The odd natural isotopes ¹⁹⁹Hg and ²⁰¹Hg are NMR-active, having spin of 1/2 and 3/2 respectively; as NMR is best with spin 1/2, the former is normally used. All isotopes of mercury are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed. These isotopes are predicted to undergo either alpha decay or double beta decay.

Daughter products other than mercury