Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has similar ductility to iron. Niobium oxidizes in 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: Niobe, daughter of Tantalus, the namesake of tantalum. The name reflects the great similarity between the two elements in their physical and chemical properties, which makes them difficult to distinguish. English chemist Charles Hatchett reported a new element similar to tantalum in 1801 and named it columbium. In 1809, English chemist William Hyde Wollaston wrongly concluded that tantalum and columbium were identical. 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. Niobium is an important addition to high-strength low-alloy steels. 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 by scavenging carbide and nitride. 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 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.

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Atomic properties

Standard atomic weight92.9063 ±1·10-5
Atomic mass92.9063 u

Atomic radii

Radius (empirical)146 pm
Radius (calculated)198 pm
Covalent radius164 ±6 pm

Atomic shell

Electron configurationKr 4d4 5s1
Ionization energy(1st) 6.75885 eV
(2nd) 14.32 eV
(3rd) 25.04 eV
(4th) 37.611 eV
(5th) 50.5728 eV
Shell model

Physical properties

Density8.57 g·cm−3 (293.1 K)
Molar volume1.083·10-5 m3·mol−1
Speed of sound3,480 m·s−1 (293.1 K)


Melting point2,750 K
Boiling point5,017 K
Liquid range2,267 K
Transition temperature9.25 K


Melting enthalpy26.8 kJ·mol-1
Enthalpy of vaporization690 kJ·mol-1
Binding energy733 kJ·mol-1

Heat and conductivity

Thermal conductivity54 W·m-1·K-1
Expansion coefficient7.3·10-6 K-1


Mohs hardness6
Brinell hardness736 NM·m-2
Vickers hardness1,320 NM·m-2

Elastic properties

Young’s modulus105 GPa
Shear modulus38 GPa
Bulk modulus170 GPa
Poisson’s ratio0.4

Electrical properties

Electrical conductivity6.58·106 S·m-1
Resistance1.52·10-7 Ωm



Chemical properties

Basicityslightly acidic
Oxidation state2, 4, 5
Standard potential-1.1 V (Nb2+ + 2e- → Nb)


Pauling scale1.6
Sanderson scale1.42
Allred-Rochow scale1.23
Ghosh-Gupta scale2.974 eV
Nagle scale1.21
Pearson absolute negativity4 eV

Other properties

Natural occurrenceprimordial
Crystal structureBody-centered cubic
Goldschmidt Classificationlithophile
Superconductorwith transition tempperature (solid body, normal pressure)
Price/kg73.5 ±12.1 USD

Natural abundances

2 ppb ≈ 2.01·1010 M☉
4 ppb ≈ 7.95·109 Mt
190 ppb ≈ 190 mg
Earth’s crust
17,000 ppb ≈ 470,000 Mt
0.001 ppb ≈ 1.37 kt