Isotopes of lanthanum

Main isotopes of lanthanum

iso NA half-life DM DE (MeV) DP 137La syn 6×104 y ε 0.600 137Ba 138La 0.089% 1.05×1011 y ε 1.737 138Ba β− 1.044 138Ce 139La 99.911% is stable with 82 neutrons
Standard atomic weight (Ar)	7002138905470000000♠138.90547(7)

Naturally occurring lanthanum (₅₇La) is composed of one stable (¹³⁹La) and one radioactive (¹³⁸La) isotope, with the stable isotope, ¹³⁹La, being the most abundant (99.91% natural abundance). There are 38 radioisotopes that have been characterized, with the most stable being ¹³⁸La, with a half-life of 102×10⁹ years; ¹³⁷La, with a half-life of 60,000 years and ¹⁴⁰La, with a half-life of 1.6781 days. The remaining radioactive isotopes have half-lives that are less than a day and the majority of these have half-lives that are less than 1 minute. This element also has 12 nuclear isomers, the longest-lived of which is ^132mLa, with a half-life of 24.3 minutes.

The isotopes of lanthanum range in atomic weight from 116.95 u (¹¹⁷La) to 154.96 u (¹⁵⁵La).

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