Niobium, 41Nb
A lump of gray shining crystals with hexagonal facetting
Pronunciationm/ (OH-bee-əm)
Appearancegray metallic, bluish when oxidized
Standard atomic weight Ar, std(Nb)92.90637(1)[1]
Niobium in the periodic table
CaesiumBariumLanthanumCeriumPraseodymiumNeodymiumPromethiumSamariumEuropiumGadoliniumTerbiumDysprosiumHolmiumErbiumThuliumYtterbiumLutetiumHafniumTantalumTungstenRheniumOsmiumIridiumPlatinumGoldMercury (element)ThalliumLeadBismuthPoloniumAstatineRadon


Atomic number (Z)41
Groupgroup 5
Periodperiod 5
Element category  Transition metal
Electron configuration[Kr] 4d4 5s1
Electrons per shell2, 8, 18, 12, 1
Physical properties
Phase at STPsolid
Melting point2750 K ​(2477 °C, ​4491 °F)
Boiling point5017 K ​(4744 °C, ​8571 °F)
Density (near r.t.)8.57 g/cm3
Heat of fusion30 kJ/mol
Heat of vaporization689.9 kJ/mol
Molar heat capacity24.60 J/(mol·K)
Vapor pressure
P (Pa)1101001 k10 k100 k
at T (K)294232073524391043935013
Atomic properties
Oxidation states−3, −1, +1, +2, +3, +4, +5 (a mildly acidic oxide)
ElectronegativityPauling scale: 1.6
Ionization energies
  • 1st: 652.1 kJ/mol
  • 2nd: 1380 kJ/mol
  • 3rd: 2416 kJ/mol
Atomic radiusempirical: 146 pm
Covalent radius164±6 pm
Color lines in a spectral range
Spectral lines of niobium
Other properties
Natural occurrenceprimordial
Crystal structurebody-centered cubic (bcc)
Cubic body-centered crystal structure for niobium
Speed of sound thin rod3480 m/s (at 20 °C)
Thermal expansion7.3 µm/(m·K)
Thermal conductivity53.7 W/(m·K)
Electrical resistivity152 nΩ·m (at 0 °C)
Magnetic orderingparamagnetic
Young's modulus105 GPa
Shear modulus38 GPa
Bulk modulus170 GPa
Poisson ratio0.40
Mohs hardness6.0
Vickers hardness870–1320 MPa
Brinell hardness735–2450 MPa
CAS Number7440-03-1
Namingafter Niobe in Greek mythology, daughter of Tantalus (tantalum)
DiscoveryCharles Hatchett (1801)
First isolationChristian Wilhelm Blomstrand (1864)
Recognized as a distinct element byHeinrich Rose (1844)
Main isotopes of niobium
Iso­topeAbun­danceHalf-life (t1/2)Decay modePro­duct
90Nbsyn15 hβ+90Zr
91Nbsyn680 yε91Zr
91mNbsyn61 dIT91Nb
92Nbtrace3.47×107 yε92Zr
92m1Nbsyn10 dε92Zr
93mNbsyn16 yIT93Nb
94Nbtrace20.3×103 yβ94Mo
95Nbsyn35 dβ95Mo
95mNbsyn4 dIT95Nb
96Nbsyn24 hβ96Mo
| references

Niobium, also known as columbium, is a chemical element with the symbol Nb (formerly Cb) and atomic number 41. Niobium is a light grey, crystalline, and ductile transition metal. Pure niobium has a hardness similar to that of pure titanium,[2][contradictory] and it has similar ductility to iron. Niobium oxidizes in the earth's atmosphere very slowly, hence its application in jewelry as a hypoallergenic alternative to nickel. Niobium is often found in the minerals pyrochlore and columbite, hence the former name "columbium". Its name comes from Greek mythology, specifically Niobe, who was the daughter of Tantalus, the namesake of tantalum. The name reflects the great similarity between the two elements in their physical and chemical properties, making them difficult to distinguish.[3]

The English chemist Charles Hatchett reported a new element similar to tantalum in 1801 and named it columbium. In 1809, the English chemist William Hyde Wollaston wrongly concluded that tantalum and columbium were identical. The German chemist Heinrich Rose determined in 1846 that tantalum ores contain a second element, which he named niobium. In 1864 and 1865, a series of scientific findings clarified that niobium and columbium were the same element (as distinguished from tantalum), and for a century both names were used interchangeably. Niobium was officially adopted as the name of the element in 1949, but the name columbium remains in current use in metallurgy in the United States.

It was not until the early 20th century that niobium was first used commercially. Brazil is the leading producer of niobium and ferroniobium, an alloy of 60–70% niobium with iron. Niobium is used mostly in alloys, the largest part in special steel such as that used in gas pipelines. Although these alloys contain a maximum of 0.1%, the small percentage of niobium enhances the strength of the steel. The temperature stability of niobium-containing superalloys is important for its use in jet and rocket engines.

Niobium is used in various superconducting materials. These superconducting alloys, also containing titanium and tin, are widely used in the superconducting magnets of MRI scanners. Other applications of niobium include welding, nuclear industries, electronics, optics, numismatics, and jewelry. In the last two applications, the low toxicity and iridescence produced by anodization are highly desired properties. Niobium is considered a technology-critical element.


Oval black and white painting of a man with a prominent shirt collar and necktie
Charles Hatchett identified the element columbium within a mineral discovered in Connecticut, US.
Black and white image of a marmor sculpture of a bowing woman with a child nestling in her lap
Picture of a Hellenistic sculpture representing Niobe by Giorgio Sommer

Niobium was identified by English chemist Charles Hatchett in 1801.[4][5][6] He found a new element in a mineral sample that had been sent to England from Connecticut, United States in 1734 by John Winthrop F.R.S. (grandson of John Winthrop the Younger) and named the mineral columbite and the new element columbium after Columbia, the poetical name for the United States.[7][8][9] The columbium discovered by Hatchett was probably a mixture of the new element with tantalum.[7]

Subsequently, there was considerable confusion[10] over the difference between columbium (niobium) and the closely related tantalum. In 1809, English chemist William Hyde Wollaston compared the oxides derived from both columbium—columbite, with a density 5.918 g/cm3, and tantalum—tantalite, with a density over 8 g/cm3, and concluded that the two oxides, despite the significant difference in density, were identical; thus he kept the name tantalum.[10] This conclusion was disputed in 1846 by German chemist Heinrich Rose, who argued that there were two different elements in the tantalite sample, and named them after children of Tantalus: niobium (from Niobe) and pelopium (from Pelops).[11][12] This confusion arose from the minimal observed differences between tantalum and niobium. The claimed new elements pelopium, ilmenium, and dianium[13] were in fact identical to niobium or mixtures of niobium and tantalum.[14]

The differences between tantalum and niobium were unequivocally demonstrated in 1864 by Christian Wilhelm Blomstrand[14] and Henri Etienne Sainte-Claire Deville, as well as Louis J. Troost, who determined the formulas of some of the compounds in 1865[14][15] and finally by Swiss chemist Jean Charles Galissard de Marignac[16] in 1866, who all proved that there were only two elements. Articles on ilmenium continued to appear until 1871.[17]

De Marignac was the first to prepare the metal in 1864, when he reduced niobium chloride by heating it in an atmosphere of hydrogen.[18] Although de Marignac was able to produce tantalum-free niobium on a larger scale by 1866, it was not until the early 20th century that niobium was used in incandescent lamp filaments, the first commercial application.[15] This use quickly became obsolete through the replacement of niobium with tungsten, which has a higher melting point. That niobium improves the strength of steel was first discovered in the 1920s, and this application remains its predominant use.[15] In 1961, the American physicist Eugene Kunzler and coworkers at Bell Labs discovered that niobium-tin continues to exhibit superconductivity in the presence of strong electric currents and magnetic fields,[19] making it the first material to support the high currents and fields necessary for useful high-power magnets and electrical power machinery. This discovery enabled – two decades later – the production of long multi-strand cables wound into coils to create large, powerful electromagnets for rotating machinery, particle accelerators, and particle detectors.[20][21]

Naming the element

Columbium (symbol "Cb")[22] was the name originally bestowed by Hatchett upon his discovery of the metal in 1801.[5] The name reflected that the type specimen of the ore came from America (Columbia).[23] This name remained in use in American journals—the last paper published by American Chemical Society with columbium in its title dates from 1953[24]—while niobium was used in Europe. To end this confusion, the name niobium was chosen for element 41 at the 15th Conference of the Union of Chemistry in Amsterdam in 1949.[25] A year later this name was officially adopted by the International Union of Pure and Applied Chemistry (IUPAC) after 100 years of controversy, despite the chronological precedence of the name columbium.[25] This was a compromise of sorts;[25] the IUPAC accepted tungsten instead of wolfram in deference to North American usage; and niobium instead of columbium in deference to European usage. While many US chemical societies and government organizations typically use the official IUPAC name, some metallurgists and metal societies still use the original American name, "columbium".[26][27][28][29]