Bismuth, 83Bi
Bismuth crystals and 1cm3 cube.jpg
Pronunciationθ/ (BIZ-məth)
Appearancelustrous brownish silver
Standard atomic weight Ar, std(Bi)208.98040(1)[1]
Bismuth in the periodic table
CaesiumBariumLanthanumCeriumPraseodymiumNeodymiumPromethiumSamariumEuropiumGadoliniumTerbiumDysprosiumHolmiumErbiumThuliumYtterbiumLutetiumHafniumTantalumTungstenRheniumOsmiumIridiumPlatinumGoldMercury (element)ThalliumLeadBismuthPoloniumAstatineRadon


Atomic number (Z)83
Groupgroup 15 (pnictogens)
Periodperiod 6
Element category  Post-transition metal
Electron configuration[Xe] 4f14 5d10 6s2 6p3
Electrons per shell2, 8, 18, 32, 18, 5
Physical properties
Phase at STPsolid
Melting point544.7 K ​(271.5 °C, ​520.7 °F)
Boiling point1837 K ​(1564 °C, ​2847 °F)
Density (near r.t.)9.78 g/cm3
when liquid (at m.p.)10.05 g/cm3
Heat of fusion11.30 kJ/mol
Heat of vaporization179 kJ/mol
Molar heat capacity25.52 J/(mol·K)
Vapor pressure
P (Pa)1101001 k10 k100 k
at T (K)94110411165132515381835
Atomic properties
Oxidation states−3, −2, −1, +1, +2, +3, +4, +5 (a mildly acidic oxide)
ElectronegativityPauling scale: 2.02
Ionization energies
  • 1st: 703 kJ/mol
  • 2nd: 1610 kJ/mol
  • 3rd: 2466 kJ/mol
  • (more)
Atomic radiusempirical: 156 pm
Covalent radius148±4 pm
Van der Waals radius207 pm
Color lines in a spectral range
Spectral lines of bismuth
Other properties
Natural occurrenceprimordial
Crystal structurerhombohedral[2]
Rhombohedral crystal structure for bismuth
Speed of sound thin rod1790 m/s (at 20 °C)
Thermal expansion13.4 µm/(m·K) (at 25 °C)
Thermal conductivity7.97 W/(m·K)
Electrical resistivity1.29 µΩ·m (at 20 °C)
Magnetic orderingdiamagnetic
Magnetic susceptibility−280.1·10−6 cm3/mol[3]
Young's modulus32 GPa
Shear modulus12 GPa
Bulk modulus31 GPa
Poisson ratio0.33
Mohs hardness2.25
Brinell hardness70–95 MPa
CAS Number7440-69-9
DiscoveryArabic alchemists (before AD 1000)
Main isotopes of bismuth
Iso­topeAbun­danceHalf-life (t1/2)Decay modePro­duct
207Bisyn31.55 yβ+207Pb
208Bisyn3.68×105 yβ+208Pb
209Bi100%2.01×1019 yα205Tl
210Bitrace5.012 dβ210Po
210mBisyn3.04×106 yIT210Bi
| references

Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a pentavalent post-transition metal and one of the pnictogens with chemical properties resembling its lighter homologs arsenic and antimony. Elemental bismuth may occur naturally, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead. It is a brittle metal with a silvery white color when freshly produced, but surface oxidation can give it a pink tinge. Bismuth is the most naturally diamagnetic element, and has one of the lowest values of thermal conductivity among metals.

Bismuth was long considered the element with the highest atomic mass that is stable, but in 2003 it was discovered to be extremely weakly radioactive: its only primordial isotope, bismuth-209, decays via alpha decay with a half-life more than a billion times the estimated age of the universe.[4][5] Because of its tremendously long half-life, bismuth may still be considered stable for almost all purposes.[5]

Main uses

Bismuth compounds account for about half the production of bismuth. They are used in cosmetics, pigments, and a few pharmaceuticals, notably bismuth subsalicylate, used to treat diarrhea.[5] Bismuth's unusual propensity to expand as it solidifies is responsible for some of its uses, such as in casting of printing type.[5] Bismuth has unusually low toxicity for a heavy metal.[5] As the toxicity of lead has become more apparent in recent years, there is an increasing use of bismuth alloys (presently about a third of bismuth production) as a replacement for lead.