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This title was formerly held by bismuth, with an atomic number of 83, until its only primordial isotope, bismuth-209, was found in 2003 to decay very slowly.The four stable isotopes of lead could theoretically undergo alpha decay to isotopes of mercury with a release of energy, but this has not been observed for any of them; their predicted half-lives range from 10 Figure 2 | The Holsinger meteorite, the largest piece of the Canyon Diablo meteorite.This is unusual; ionization energies generally fall going down a group, as an element's outer electrons become more distant from the nucleus, and more shielded by smaller orbitals.The similarity of ionization energies is caused by the lanthanide contraction—the decrease in element radii from lanthanum (atomic number 57) to lutetium (71), and the relatively small radii of the elements after hafnium (72).Lead production declined after the fall of Rome and did not reach comparable levels until the Industrial Revolution.
When freshly cut, lead is silvery with a hint of blue; it tarnishes to a dull gray color when exposed to air.
Lead is easily extracted from its ores; prehistoric people in Western Asia knew of it.
Galena, a principal ore of lead, often bears silver, interest in which helped initiate widespread extraction and use of lead in ancient Rome.
Lead has the highest atomic number of any stable element and concludes three major decay chains of heavier elements.
Lead is a relatively unreactive post-transition metal.