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Lead

Chemical element, symbol Pb and atomic number 82 / From Wikipedia, the free encyclopedia

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Lead is a chemical element; it has symbol Pb (from Latin plumbum) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray color when exposed to air. Lead has the highest atomic number of any stable element and three of its isotopes are endpoints of major nuclear decay chains of heavier elements. Lead is toxic, even in small amounts, especially to children.

Quick facts: Lead, Pronunciation, Appearance, Standard ato...
Lead, 82Pb
A small gray metal cube surrounded by three gray metal nuggets in front of a light gray background
Lead
Pronunciation/ˈlɛd/ (led)
Appearancemetallic gray
Standard atomic weight Ar°(Pb)
  • [206.14, 207.94]
  • 207.2±1.1 (abridged)[1]
Lead in the periodic table
Sn

Pb

Fl
thalliumleadbismuth
Atomic number (Z)82
Groupgroup 14 (carbon group)
Periodperiod 6
Block  p-block
Electron configuration[Xe] 4f14 5d10 6s2 6p2
Electrons per shell2, 8, 18, 32, 18, 4
Physical properties
Phase at STPsolid
Melting point600.61 K (327.46 °C, 621.43 °F)
Boiling point2022 K (1749 °C, 3180 °F)
Density (near r.t.)11.34 g/cm3
when liquid (at m.p.)10.66 g/cm3
Heat of fusion4.77 kJ/mol
Heat of vaporization179.5 kJ/mol
Molar heat capacity26.650 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 978 1088 1229 1412 1660 2027
Atomic properties
Oxidation states−4, −2, −1, 0,[2] +1, +2, +3, +4 (an amphoteric oxide)
ElectronegativityPauling scale: 2.33 (in +4), 1.87 (in +2)
Ionization energies
  • 1st: 715.6 kJ/mol
  • 2nd: 1450.5 kJ/mol
  • 3rd: 3081.5 kJ/mol
Atomic radiusempirical: 175 pm
Covalent radius146±5 pm
Van der Waals radius202 pm
Color lines in a spectral range
Spectral lines of lead
Other properties
Natural occurrenceprimordial
Crystal structure face-centered cubic (fcc)
Face-centered cubic crystal structure for lead

a=495.08 pm
Speed of sound thin rod1190 m/s (at r.t.) (annealed)
Thermal expansion28.9 µm/(m⋅K) (at 25 °C)
Thermal conductivity35.3 W/(m⋅K)
Electrical resistivity208 nΩ⋅m (at 20 °C)
Magnetic orderingdiamagnetic
Molar magnetic susceptibility−23.0×10−6 cm3/mol (at 298 K)[3]
Young's modulus16 GPa
Shear modulus5.6 GPa
Bulk modulus46 GPa
Poisson ratio0.44
Mohs hardness1.5
Brinell hardness38–50 MPa
CAS Number7439-92-1
History
DiscoveryMiddle East (7000 BCE)
Symbol"Pb": from Latin plumbum
Isotopes of lead
Main isotopes[4] Decay
abun­dance half-life (t1/2) mode pro­duct
202Pb synth 5.25×104 y ε 202Tl
204Pb 1.40% stable
205Pb trace 1.73×107 y ε 205Tl
206Pb 24.1% stable
207Pb 22.1% stable
208Pb 52.4% stable
209Pb trace 3.253 h β 209Bi
210Pb trace 22.20 y β 210Bi
211Pb trace 36.1 min β 211Bi
212Pb trace 10.64 h β 212Bi
214Pb trace 26.8 min β 214Bi
Isotopic abundances vary greatly by sample[5]
Symbol_category_class.svg Category: Lead
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Lead is a relatively unreactive post-transition metal. Its weak metallic character is illustrated by its amphoteric nature; lead and lead oxides react with acids and bases, and it tends to form covalent bonds. Compounds of lead are usually found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group. Exceptions are mostly limited to organolead compounds. Like the lighter members of the group, lead tends to bond with itself; it can form chains and polyhedral structures.

Since lead is easily extracted from its ores, prehistoric people in the Near East were aware of it. Galena is a principal ore of lead which often bears silver. Interest in silver helped initiate widespread extraction and use of lead in ancient Rome. Lead production declined after the fall of Rome and did not reach comparable levels until the Industrial Revolution. Lead played a crucial role in the development of the printing press, as movable type could be relatively easily cast from lead alloys.[6] In 2014, the annual global production of lead was about ten million tonnes, over half of which was from recycling. Lead's high density, low melting point, ductility and relative inertness to oxidation make it useful. These properties, combined with its relative abundance and low cost, resulted in its extensive use in construction, plumbing, batteries, bullets and shot, weights, solders, pewters, fusible alloys, white paints, leaded gasoline, and radiation shielding.

Lead is a devastating and persistent neurotoxin that accumulates in soft tissues and bones. It damages the nervous system and interferes with the function of biological enzymes, causing neurological disorders ranging from behavioral problems to brain damage, and also affects general health, cardiovascular, and renal systems. Lead's toxicity was first documented by ancient Greek and Roman writers, who noted some of the symptoms of lead poisoning, but became widely recognized in Europe in the late 19th century.

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