Lead206

Lead-206 (Pb-206) is a stable isotope of the element lead. It has 82 protons and 124 neutrons, giving a mass number of 206. As an even-even nucleus, its ground-state spin is 0+ and it does not undergo radioactive decay.

In nature, lead consists of four stable isotopes, including Pb-206. Its natural abundance is about 24% of total lead, with Pb-204 around 1.4%, Pb-207 about 22%, and Pb-208 about 52%.

Pb-206 is the stable end product of the uranium-238 decay series, arising from the long chain of decays starting with 238U. A portion of lead-206 in rocks and minerals also reflects primordial lead and radiogenic contributions. Because the Pb-206 fraction changes only via radioactive decay over geological timescales, the ratios among lead isotopes are widely used in geochronology and cosmochemistry.

Pb-206 is central to lead-lead dating methods, including concordia plots and model dating, which compare 206Pb/204Pb and 207Pb/204Pb ratios to determine crystallization ages of rocks, minerals such as zircon, and meteorites. It also features in studies of the Earth's age and the timing of crust formation.