It is particularly problematic in children: even if blood levels are promptly normalized with treatment, neurological disorders, such as brain damage and behavioral problems, may result. The sum of lead's first and second ionization energies—the total energy required to remove the two 6p electrons—is close to that of tin, lead's upper neighbor in the carbon group.
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.
This is due to poor shielding of the nucleus by the lanthanide 4f electrons.
Lead is a chemical element with symbol Pb (from the Latin plumbum) and atomic number 82.
It is a heavy metal that is denser than most common materials.
The sum of the first four ionization energies of lead exceeds that of tin, Lead's lighter carbon group congeners form stable or metastable allotropes with the tetrahedrally coordinated and covalently bonded diamond cubic structure.
The energy levels of their outer s- and p-orbitals are close enough to allow mixing into four hybrid sp orbitals.
Lead has the highest atomic number of any stable element and three of its isotopes each conclude a major decay chain of heavier elements.
Lead is a relatively unreactive post-transition metal.
Lead-211, -212, and -214 are present in the decay chains of uranium-235, thorium-232, and uranium-238, respectively, so traces of all three of these lead isotopes are found naturally.
Minute traces of lead-209 arise from the very rare cluster decay of radium-223, one of the daughter products of natural uranium-235, and the decay chain of neptunium-237, traces of which are produced by neutron capture in uranium ores.
Apart from the stable isotopes, which make up almost all lead that exists naturally, there are trace quantities of a few radioactive isotopes.
One of them is lead-210; although it has a half-life of only 22.3 years, small quantities occur in nature because lead-210 is produced by a long decay series that starts with uranium-238 (which has been present for billions of years on Earth).