210pb dating wiki

17-Jan-2018 13:25

Lead is soft and malleable, and has a relatively low melting point.When freshly cut, lead is bluish-white; it tarnishes to a dull gray color when exposed to air.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 combined first four ionization energies of lead exceed those 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.In lead, the inert pair effect increases the separation between its s- and p-orbitals, and the gap cannot be overcome by the energy that would be released by extra bonds following hybridization.It tarnishes on contact with moist air, and takes on a dull appearance the hue of which depends on the prevailing conditions.

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Lead's tensile strength, at 12–17 MPa, is low (that of aluminium is 6 times higher, copper 10 times, and mild steel 15 times higher); it can be strengthened by adding small amounts of copper or antimony. The electrical resistivity of lead at 20 °C is 192 nanoohm-meters, almost an order of magnitude higher than those of other industrial metals (copper at 15.43 nΩ·m; gold 20.51 nΩ·m; and aluminium at 24.15 nΩ·m).

In the late 19th century, lead's toxicity was recognized, and its use has since been phased out of many applications.