Isotopes of lead

²⁰⁶Pb is the final step in the decay chain of ²³⁸U, the "radium series" or "uranium series". In a closed system, over time, a given mass of ²³⁸U will decay in a sequence of steps culminating in ²⁰⁶Pb. The production of intermediate products eventually reaches an equilibrium (though this takes a long time, as the half-life of ²³⁴U is 245,500 years). Once this stabilized system is reached, the ratio of ²³⁸U to ²⁰⁶Pb will steadily decrease, while the ratios of the other intermediate products to each other remain constant.

Like most radioisotopes found in the radium series, ²⁰⁶Pb was initially named as a variation of radium, specifically radium G. It is the decay product of both ²¹⁰Po (historically called radium F) by alpha decay, and the much rarer ²⁰⁶Tl (radium E^II) by beta decay.

Lead-206 has been proposed for use in fast breeder nuclear fission reactor coolant over the use of natural lead mixture (which also includes other stable lead isotopes) as a mechanism to improve neutron economy and greatly suppress unwanted production of highly radioactive byproducts.^[13]

²⁰⁴Pb is entirely primordial, and is thus useful for estimating the fraction of the other lead isotopes in a given sample that are also primordial, since the relative fractions of the various primordial lead isotopes is constant everywhere.^[14] Any excess lead-206, -207, and -208 is thus assumed to be radiogenic in origin,^[14] allowing various uranium and thorium dating schemes to be used to estimate the age of rocks (time since their formation) based on the relative abundance of lead-204 to other isotopes.²⁰⁷Pb is the end of the actinium series from ²³⁵U.

²⁰⁸Pb is the end of the thorium series from ²³²Th. While it only makes up approximately half of the composition of lead in most places on Earth, it can be found naturally enriched up to around 90% in thorium ores.^{[15] 208}Pb is the heaviest known stable nuclide and also the heaviest known doubly magic nucleus, as Z = 82 and N = 126 correspond to closed nuclear shells.^[16] As a consequence of this particularly stable configuration, its neutron capture cross section is very low (even lower than that of deuterium in the thermal spectrum), making it of interest for lead-cooled fast reactors.

²¹²Pb-containing radiopharmaceuticals have been trialed as therapeutic agents for the experimental cancer treatment targeted alpha-particle therapy.^[17]

• Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.

Isotope masses from:

• Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001

Half-life, spin, and isomer data selected from the following sources.

• Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
• National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
• Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.