Isotopes of lead

Isotopes of lead (82Pb)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
202Pb synth 5.25×104 y ε 202Tl
204Pb 1.40% stable
205Pb synth 1.70×107 y ε 205Tl
206Pb 24.1% stable
207Pb 22.1% stable
208Pb 52.4% stable
209Pb trace 3.235 h β− 209Bi
210Pb trace 22.2 y β− 210Bi
α 206Hg
211Pb trace 36.16 min β− 211Bi
212Pb trace 10.627 h β− 212Bi
214Pb trace 27.06 min β− 214Bi
Isotopic abundances vary greatly by sample[2]
Standard atomic weight Ar°(Pb)

Lead (82Pb) has four observationally stable isotopes: 204Pb, 206Pb, 207Pb, 208Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide. The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains: the uranium series (or radium series), the actinium series, and the thorium series, respectively; a fourth decay chain, the neptunium series, terminates with the thallium isotope 205Tl. The three series terminating in lead represent the decay chain products of long-lived primordial 238U, 235U, and 232Th. Each isotope also occurs, to some extent, as primordial isotopes that were made in supernovae, rather than radiogenically as daughter products. The fixed ratio of lead-204 to the primordial amounts of the other lead isotopes may be used as the baseline to estimate the extra amounts of radiogenic lead present in rocks as a result of decay from uranium and thorium. (See lead–lead dating and uranium–lead dating.)

The longest-lived radioisotopes, both decaying by electron capture, are 205Pb with a half-life of 17.3 million years and 202Pb with a half-life of 52,500 years. A shorter-lived naturally occurring radioisotope, 210Pb with a half-life of 22.2 years, is useful for studying the sedimentation chronology of environmental samples on time scales shorter than 100 years.[5]

The heaviest stable isotope, 208Pb, belongs to this element. (The more massive 209Bi, long considered to be stable, actually has a half-life of 2.01×1019 years.) 208Pb is also a doubly magic isotope, as it has 82 protons and 126 neutrons.[6] It is the heaviest doubly magic nuclide known.

The four primordial isotopes of lead are all observationally stable, meaning that they are predicted to undergo radioactive decay but no decay has been observed yet. These four isotopes are predicted to undergo alpha decay and become isotopes of mercury which are themselves radioactive or observationally stable.

There are trace quantities existing of the radioactive isotopes 209-214. The largest and most important is lead-210 as it has by far the longest half-life (22.2 years) and occurs in the abundant uranium decay series. Lead-211, −212, and −214 are present in the decay chains of uranium-235, thorium-232, and uranium-238, further, making these three lead isotopes also detectable in natural sources. The more minute traces of lead-209 arise from three rare decay branches: by frequency, the rare beta-minus-neutron decay of thallium-210 (in the uranium series), the last step of the neptunium series, traces of which are produced by neutron capture in uranium ores, and the very rare cluster decay of radium-223 (yielding also carbon-14). Lead-213 also occurs in a branch of the neptunium series. Lead-210 is particularly useful for helping to identify the ages of samples by measuring its ratio to lead-206 (both isotopes are present in a single decay chain).[7]

In total, 43 lead isotopes have been synthesized, from 178Pb to 220Pb.

  1. ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. ^ Meija et al. 2016.
  3. ^ "Standard Atomic Weights: Lead". CIAAW. 2020.
  4. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  5. ^ Jeter, Hewitt W. (March 2000). "Determining the Ages of Recent Sediments Using Measurements of Trace Radioactivity" (PDF). Terra et Aqua (78): 21–28. Archived from the original (PDF) on March 4, 2016. Retrieved October 23, 2019.
  6. ^ Blank, B.; Regan, P.H. (2000). "Magic and doubly-magic nuclei". Nuclear Physics News. 10 (4): 20–27. doi:10.1080/10506890109411553. S2CID 121966707.
  7. ^ Fiorini 2010, pp. 7–8.
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