Isotopes Of Lead
Lead (Pb) has four 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 called the uranium series (or radium series), the actinium series, and the thorium series, respectively. These series represent the decay chain products of long-lived primoridal U-238, U-235, and Th-232, respectively. However, each of them also occurs, to some extent, as primordial isotopes which 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 are 205Pb with a half-life of ~15.3 million years and 202Pb with a half-life of ~53,000 years. Of naturally-occurring radioisotopes, the longest half-life is 210Pb with a half-life of 22.20 years.
The standard atomic mass (abundance-weighted average of the stable isotopes) is 207.2(1) u. Lead is the element with the heaviest stable isotope, 208Pb. (The more massive 209Bi, long considered to be stable, actually has a half-life of 1.9×1019 years). A total of 38 Pb isotopes are now known, including very unstable synthetic species.
Read more about Isotopes Of Lead: Lead-206, Lead 207, 208, and 204, Table
Famous quotes containing the word lead:
“The greatest, or rather the most prominent, part of this city was constructed with the design to offer the deadest resistance to leaden and iron missiles that might be cast against it. But it is a remarkable meteorological and psychological fact, that it is rarely known to rain lead with much violence, except on places so constructed.”
—Henry David Thoreau (1817–1862)