Lead (Pb)

Stable isotopes of lead available from ISOFLEX

Isotope Z(p) N(n) Atomic Mass Natural Abundance Enrichment Level Chemical Form
Pb-204  82  122  203.973028 1.40%  99.90% Metal
Pb-204 82 122 203.973028 1.40% 99.90% Oxide
Pb-206 82 124 205.974449 24.10% >99.00% Metal
Pb-206 82 124 205.974449 24.10% >99.00% Oxide
Pb-207 82 125 206.975880 22.10% 72.00->99.00% Metal
Pb-207 82 125 206.975880 22.10% 72.00->99.00% Oxide
Pb-208  82  126  207.976636 52.40%  97.80->99.50% Metal
Pb-208 82 126 207.976636 52.40% 97.80->99.50% Oxide

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Pb

Lead has been known and used throughout history — ancient alchemists believed it was the world's oldest metal and devoted a great deal of time attempting to transmute it into gold. Its name originates with the Anglo-Saxon word lead, and its symbol — Pb — with the Latin word plumbum, meaning “liquid silver.”

Lead is a heavy, very soft, malleable, ductile solid with face-centered cubic crystals. It is soluble in dilute nitric acid and insoluble in water (but dissolves slowly in water containing a weak acid). It resists corrosion and is relatively impenetrable to radiation. It is a poor electrical conductor. Lead forms amphoteric compounds in +2 and +4 valence states, forming plumbous and plumbic salts, as well as plumbites and plumbates. Its divalent compounds are far more numerous than its tetravalent compounds. In its very finely divided form, lead is pyrophoric. The metal is not attacked by hot water; in hard water, however, the presence of small amounts of carbonate, sulfate or silicate ions forms a protective film on the metal's surface. Lead does not evolve hydrogen readily with acids. At ordinary temperatures, it is not readily attacked by sulfuric acid. Hydrofluoric acid also has little action on the metal. Organic acids in the presence of oxygen react slowly with lead, forming their soluble salts; thus acetic acid in the presence of oxygen forms lead(II) acetate. Lead combines with fluorine, chlorine and bromine, forming bivalent lead halides.

There are numerous applications for lead in all its forms: metal, alloys and compounds. It is useful in the construction of pipelines, plumbing fixtures, wires, ammunition, containers for corrosive acids, and as a shield against short-wavelength radiation. Both the metal and its dioxide are used in storage batteries. Several lead compounds — such as lead chromate, lead sulfate, lead tetroxide and the basic carbonate — have been used in paint.

Considered an acute and chronic toxicant, lead can cause acute ataxia, headache, vomiting, stupor, hallucination, tremors and convulsions, along with chronic symptoms including weight loss, anemia, kidney damage, memory loss and brain damage. 

Properties of Lead

Name Lead 
Symbol Pb 
Atomic number 82 
Atomic weight 207.2
Standard state Solid at 298 °K 
CAS Registry ID 7439-92-1 
Group in periodic table 14 
Group name None 
Period in periodic table 6 
Block in periodic table p-block 
Color Bluish white 
Classification Metallic 
Melting point 327.46 °C
Boiling point 1740 °C
Thermal conductivity 35.3 W/(m·K) at 298.2 °K
Electrical resistivity 20.65 µΩ·cm at 20 °C 
Electronegativity 1.8 
Specific heat 0.128 J/(g·K) at 20 °C
Heat of vaporization 178 kJ·mol-1 at 1740 °C
Heat of fusion 4.77 kJ·mol-1
Density of liquid 10.66 g/cm3 at 327.46 °C 
Density of solid 11.3 g/cm3
Mohs hardness scale 1
Electron configuration [Xe]4f145d106s26p2 
Atomic radius 1.75 Å 
Covalent radius (sp3) 1.44 Å
Ionic radius  Pb2+: 1.18 Å; Pb4+: 0.70 Å
Oxidation states  +2, +4 

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