• Asbestos
• Mildew
• Mold
• Radon

Lead

For the "lead" in news writing, see news style.

thallium - lead - bismuth Sn Pb Uuq       Full table
General
Name, Symbol, Number	Lead, Pb, 82
Chemical series	Poor metals
Group, Period, Block	14(IVA), 6 , p
Density, Hardness	11340 kg/m3, 1.5
Appearance	bluish white
Atomic properties
Atomic weight	207.2 amu
Atomic radius (calc.)	180 (154) pm
Covalent radius	147 pm
van der Waals radius	202 pm
Electron configuration	[Xe]4*4f14 5d10 6s2 6p2
e- 's per energy level	2, 8, 18, 32, 18, 4
Oxidation states (Oxide)	4, 2 (amphoteric)
Crystal structure	Cubic face centered
Physical properties
State of matter	Solid
Melting point	600.61 K (621.43 °F)
Boiling point	2022 K (3180 °F)
Molar volume	18.26 ×10;10-6 m3/mol
Heat of vaporization	177.7 kJ/mol
Heat of fusion	4.799 kJ/mol
Vapor pressure	4.21 E-07 Pa at 600 K
Speed of sound	1260 m/s at 293.15 K
Miscellaneous
Electronegativity	2.33 (Pauling scale)
Specific heat capacity	129 J/(kg*K)
Electrical conductivity	4.81 106/m ohm
Thermal conductivity	35.3 W/(m*K)
1st ionization potential	715.6 kJ/mol
2nd ionization potential	1450.5 kJ/mol
3rd ionization potential	3081.5 kJ/mol
4th ionization potential	4083 kJ/mol
5th ionization potential	6640 kJ/mol
Most stable isotopes
iso NA half-life DM DE MeV DP 202Pb {syn.} 52500 y Alpha Epsilon 2.598 0.050 198Hg 202Tl 204Pb 1.4 >1.4 E17 y Alpha 2.186 200Hg 205Pb {syn.} 1.53 E7 y Epsilon 0.051 205Tl 206Pb 24.1% Pb is stable with 124 neutrons 207Pb 22.1% Pb is stable with 125 neutrons 208Pb 52.4% Pb is stable with 126 neutrons 210Pb {syn.} 22.3 y Alpha Beta 3.792 0.064 206Hg 210Bi
SI units & STP are used except where noted.

Lead is a chemical element in the periodic table that has the symbol Pb and atomic number 82. A soft, heavy, toxic and malleable poor metal, lead has a dull gray appearance and is bluish white when freshly cut but tarnishes to dull gray when exposed to air. Lead is used in building construction, lead-acid accumulators, bullets and shot, and is part of solder, pewter, and fusible alloys. Lead has the highest atomic number of all stable elements.*

Table of contents

1 Notable characteristics 2 Applications 3 History 4 Extraction 5 Isotopes 6 Precautions 7 Language derivations 8 Reference 9 External links

Notable characteristics

Applications

• in lead-acid batteries, in electronic components, cable sheathing, ammunition, in the glass of CRTs, ceramics, leaded glass (see glass making), lead piping (not much used these days, although leaded solder was legal for use on drinking water pipes into the 1980s (US)), in paint (banned since 1978 in the US, and gradually in the UK from the 1950s to the 1970s, although older painted surfaces could be up to 50% lead by weight), casting alloys, pewter, solder, and dentistry filling. Also used as flashing on roofing to protect joins from rain. In gasoline (petrol) as tetra-ethyl lead and tetra-methyl lead to reduce knocking (also called pre-detonation, pre-ignition or pinking) from the 1920s, in 1986 leaded gasoline was banned from sale in the United States, in the EU in 1999.

History

By the mid-1980s, a significant shift in lead end-use patterns had taken place. Much of this shift was a result of the U.S. lead consumers' compliance with environmental regulations that significantly reduced or eliminated the use of lead in nonbattery products, including gasoline, paints, solders, and water systems.

Extraction

In mining, the ore is extracted by drilling or blasting and then crushed and ground. The ore is then taken through a process developed in Australia in the 19th century at Broken Hill. A flotation process separates the lead and other minerals from the waste rock (tailings) to form a concentrate by passing the ore, water and certain chemicals through a series of tanks in which the slurry is constantly mixed. Air is blown through the tanks and lead sulphides attach to the bubbles and rise to form a foam which can be removed. The foam (which is around 50% lead) is dried and then sintered before being smelted to produce a 97% lead concentrate. The lead is then cooled in stages which causes the lighter impurites (dross) to rise to the surface where they can be removed. The molten lead bullion is then refined by additional smelting with air being passed over the lead to form a slag layer containing any remaining impurities and producing 99.9% pure lead.

Isotopes

Precautions

The concern about lead's role in mental retardation in children has brought about widespread reduction in its use (lead exposure has been linked to schizophrenia). Paint containing lead has been withdrawn from sale in industralised countries, though many older houses may still contain substantial lead in their old paint: it is generally recommended that old paint should not be stripped by sanding, as this generates inhalable dust.

Lead salts used in pottery glazes have on occasion caused poisoning, when acid drinks, such as fruit juices, have leached lead ions out of the glaze. It has been suggested that what was known as "Devon colic" arose from the use of lead-lined presses to extract apple juice in the manufacture of cider. Lead is considered to have particularly nasty consequences for mothers in spe, i.e. girls and young women. For that reason many universities do not hand out lead containing samples to girls for instructional laboratory analyses.

The earliest pencils actually used lead, though 'pencil leads' have been made for the last couple of centuries from graphite, a naturally occurring form (allotrope) of carbon.

See also: lead poisoning

Language derivations

• Plumbing, or system of piping, derives from the fact that pipes were once made of lead.
• Plumb bob or plummet, a small, pointed body of metal the weight of which is used to draw a string vertical under tension, refers to the fact that they were originally made from lead.
• Plumb wall is so-said because a plumb bob is used to find the vertical.
• Plumbing the depths derives from the use of the lead weight to draw the sounding line down to the bottom of the water body (or to the end of the line if the water's really deep!).
• Plumb crazy may derive from the fact that lead poisoning can cause insanity; or, according to the OED, from a U.S. sense of plum (derived from plumb) meaning 'completely'.
• Plumbism is the medical term for lead poisoning.
• Aplomb comes from the French à plomb, meaning plumb vertical, and therefore confident and cool.

Bismuth-209 has a half-life of the order of a billion times the believed age of the universe and is sometimes considered stable, thus sometimes bismuth is considered to have the highest atomic number of all stable elements.

Reference

• Los Alamos National Laboratory - Lead

• WebElements.com - Lead
• EnvironmentalChemistry.com - Lead
• Global Phaseout of Leaded Gasoline

Source | Copyright