Antimony-121

Main isotopes of antimony

Iso­tope Decay abun­dance half-life mode energy (MeV) pro­duct 121Sb 57.21% is stable with 70 neutrons 123Sb 42.79% is stable with 72 neutrons 125Sb syn 2.7582 y β− 0.767 125Te
Standard atomic weight (Ar)	121.760(1)

Antimony (₅₁Sb) occurs in two stable isotopes, ¹²¹Sb and ¹²³Sb. There are 35 artificial radioactive isotopes, the longest-lived of which are ¹²⁵Sb, with a half-life of 2.75856 years; ¹²⁴Sb, with a half-life of 60.2 days; and ¹²⁶Sb, with a half-life of 12.35 days. All other isotopes have half-lives less than 4 days, most less than an hour.

There are also many isomers, the longest-lived of which is ^120m1Sb with a half-life of 5.76 days.

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