Isotopes of promethium

36 radioisotopes of Promethium (Pm) have been characterized, with the most stable being ¹⁴⁵Pm with a half-life of 17.7 years, ¹⁴⁶Pm with a half-life of 5.53 years, and ¹⁴⁷Pm with a half-life of 2.6234 years. All of the remaining radioactive isotopes have half-lives that are less than 364 days, and the majority of these have half lives that are less than 27 seconds. This element also has 11 meta states with the most stable being ¹⁴⁸Pm^m (T_½ 41.29 days), ¹⁵²Pm^m2 (T_½ 13.8 minutes) and ¹⁵²Pm^m (T_½ 7.52 minutes).

The isotopes of promethium range in atomic weight from 127.9482600 u (¹²⁸Pm) to 162.9535200 u (¹⁶³Pm). The primary decay mode before the longest-lived isotope, ¹⁴⁵Pm, is electron capture, and the primary mode after is beta minus decay. The primary decay products before ¹⁴⁵Pm are neodymium (Nd) isotopes and the primary products after are samarium (Sm) isotopes.

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Stability of promethium isotopes

Beside technetium, promethium is one of the two elements with atomic number less than 83 that have only unstable isotopes, which is a rarely occurring effect of the liquid drop model and stabilities of neighbor element isotopes.

Has no stable isotopes. A standard atomic mass cannot be given.

Table

Notes

• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References

• Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
• Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure Appl. Chem. Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).
• Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
  • Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128 (2003).
  • National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (retrieved Sept. 2005).
  • David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.