205Pb

Lead-205 (205Pb) is a radioactive isotope of lead with a mass number of 205. It is not one of the naturally abundant lead isotopes and occurs only in trace amounts in nature; it is primarily produced for research purposes in nuclear facilities or through targeted production in laboratories.

Nuclear properties of 205Pb include a long half-life, typically cited around the order of 10 to 20 million years. It decays by electron capture to the stable isotope 205Tl (thallium-205), with emitted radiation including low-energy gamma rays and X-rays accompanying the capture process. The daughter nuclide, 205Tl, is a stable isotope of thallium.

Natural occurrence and production methods: 205Pb is not found in significant quantities in ordinary geological materials. It is generated in nuclear reactions, most commonly by neutron capture on 204Pb (204Pb(n, γ)205Pb) in reactors or via accelerator-based spallation processes. Because of its long half-life and scarcity, 205Pb is typically produced specifically for experimental use rather than occurring as a readily available natural resource.

Applications and utilization: In research settings, 205Pb serves as a radiotracer and as a tool for studying neutron capture cross sections, decay schemes, and lead isotope systematics in geochemistry and cosmochemistry. Its long half-life makes it useful for certain time-scale investigations, while its production requires controlled laboratory conditions. It is not widely employed for routine radiometric dating in the same way as the major lead isotopes (204Pb, 206Pb, 207Pb, 208Pb), but it contributes to specialized studies of nucleosynthesis and trace element behavior.

Safety: As a long-lived radionuclide, handling of 205Pb requires appropriate radiological controls, shielding, and waste management in line with applicable regulations.