Pb238

Pb‑238 is a radioactive isotope of lead with an atomic number of 82 and a mass number of 238. It contains 82 protons and 156 neutrons and is situated in the decay series of uranium‑238, where it appears as a short‑lived intermediate product. The isotope is not naturally abundant; it is primarily produced in laboratory settings through neutron capture on stable Pb‑207 or as a decay product of heavier actinides such as Bi‑238.

The half‑life of Pb‑238 is on the order of minutes, leading to rapid decay by beta emission to bismuth‑238, which subsequently decays to polonium‑238 and ultimately to the stable isotope lead‑206. Its decay energy is modest, and the emitted beta particles have low penetrating power, limiting external radiation hazards but requiring careful handling in research environments.

Physical properties of Pb‑238 are similar to those of other lead isotopes, including a metallic luster, high density, and low melting point relative to its atomic mass. However, the short half‑life precludes bulk applications; the isotope is mainly of interest for scientific investigations of nuclear decay pathways, cross‑section measurements, and as a tracer in studies of nuclear fuel cycles.

Because of its fleeting existence, Pb‑238 does not accumulate in the environment and poses minimal radiological risk outside controlled experimental contexts. Its detection is typically achieved through gamma spectroscopy, where characteristic emissions from its decay progeny provide indirect identification. Research on Pb‑238 contributes to a broader understanding of heavy‑element nucleosynthesis and the behavior of transuranic decay chains.