Lead isotopes are variations of the element lead that have the same number of protons but different numbers of neutrons. The most common isotopes of lead are lead-204, lead-206, lead-207, and lead-208. These isotopes are stable and do not undergo radioactive decay, making them useful in various scientific applications. Lead isotopes are often used in geochronology to date rocks and minerals. By analyzing the ratios of lead isotopes, scientists can determine the age of a sample and gain insights into the history of the Earth. Additionally, lead isotopes play a role in nuclear physics and environmental studies.