Niobium

 Atomic Number:

41

 Melting Point: 2477 ºC
Atomic Symbol: Nb Boiling Point:  4744 ºC
Atomic Weight: 92.9064 amu Density: 8570 kg/m 3
Atomic Radius:

142.9 pm

 Oxidation States: 5, 3
Covalent Radius: 137 pm Electron Configuration: [Kr]5s14d4
van der Waals Radius:

--

 State of Matter: solid 

History

(Named after Niobe, the daughter of Tantalus) Discovered in 1801 by Hatchett in an ore sent to England.  The metal was first prepared in 1864 by Blomstrand, who reduced the chloride by heating it in a hydrogen atmosphere. The name niobium was adopted by the International Union of Pure and Applied Chemicstry (IUPAC) in 1950 after 100 years of controversy. Many leading chemical societies and government organizations refer to it by this name. Most metallurgists, leading metal societies, and all but one of the leading U.S. commercial producers, however, still refer to the metal as "columbium."

Properties

Niobium is a shiny, white, soft, and ductile metal, and takes on a bluish cast when exposed to air at room temperatures for a long time. The metal starts to oxidize in air at 200oC, and when processed at even moderate temperatures must be placed in a protective atmosphere.

Sources

The element is found in niobite (or columbite), niobite-tantalite, parochlore, and euxenite. Large deposits of niobium have been found associated with carbonatites (carbon-silicate rocks), as a constituent of parochlore. Extensive ore reserves are found in Canada, Brazil, Nigeria, Zaire, and in Russia.

Uses

Niobium is used in arc-welding rods for stabilized grades of stainless steel. Appreciable amounts of niobium in the form of high-purity ferroniobium and nickel niobium are used in nickel-, cobalt-, and iron-base superalloys for such applications as jet engine components, rocket subassemblies, and heat-resisting and combustion equipment. For example, advanced air frame systems such as those used in the Gemini program used this metal.

Niobium becomes a superconductor when lowered to cryogenic temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors, 9.3 K. In addition, it is one of the three elemental superconductors that are Type II (the others being vanadium and technetium), meaning it remains a superconductor when subjected to high magnetic fields. Niobium-tin and niobium-titanium alloys are used as wires for superconducting magnets capable of producing exceedingly strong magnetic fields.

The metal has a low capture cross-section for thermal neutrons and so finds use in the nuclear industries. Because of its bluish color, niobium is also used in body piercing jewelry (usually as an alloy). It is also being evaluated as an alternative to tantalum in capacitors.

Niobium is a component of some stainless steels and an alloy of other nonferrous metals. These alloys are strong and are often used in pipeline construction.

Isotopes

Eighteen isotopes of niobium are known. The metal can be isolated from tantalum, and prepared in several ways.

Hazards

Niobium containing compounds are relatively rarely encountered by most people but many are highly toxic and should be treated with care. Metallic niobium dust is an eye and skin irritant and also can be a fire hazard. Niobium has no biological role.