|Name, Symbol, Number||Niobium, Nb, 41|
|Chemical series||Transition metals|
|Group, Period, Block||5, 5 , d|
|Density, Hardness||8570 kg/m3, 6|
|Atomic weight||92.90638 amu|
|Atomic radius (calc.)||145 (198) pm|
|Covalent radius||137 pm|
|van der Waals radius||no data|
|Electron configuration||[Kr]4d4d4 5s1|
|e- 's per energy level||2, 8, 18, 12, 1|
|Oxidation states (Oxide)||5, 3 (mildly acidic)|
|Crystal structure||Cubic body centered|
|State of matter||solid (__)|
|Melting point||2750 K (4491 °F)|
|Boiling point||5017 K (8571 °F)|
|Molar volume||10.83 ×1010-3 m3/mol|
|Heat of vaporization||696.6 kJ/mol|
|Heat of fusion||26.4 kJ/mol|
|Vapor pressure||0.0755 Pa at 2741 K|
|Speed of sound||3480 m/s at 293.15 K|
|Electronegativity||1.6 (Pauling scale)|
|Specific heat capacity||265 J/(kg*K)|
|Electrical conductivity||6.93 106/m ohm|
|Thermal conductivity||53.7 W/(m*K)|
|1st ionization potential||652.1 kJ/mol|
|2nd ionization potential||1380 kJ/mol|
|3rd ionization potential||2416 kJ/mol|
|4th ionization potential||3700 kJ/mol|
|5th ionization potential||4877 kJ/mol|
|6th ionization potential||9847 kJ/mol|
|7th ionization potential||12100 kJ/mol|
|Most Stable Isotopes|
|SI units & STP are used except where noted.|
|Table of contents|
7 External Links
Niobium is a shiny grey, ductile metal that takes on a bluish tinge when exposed to air at room temperature for extended periods. Niobium's chemical properties are almost identical to the chemical properties of tantalum, which appears below niobium in the periodic table.
When it is processed at even moderate temperatures niobium must be placed in a protective atmosphere. The metal begins to oxidize in air at 200 ° C and its oxidation states are +2, +3, +5.
Niobium has a number of uses: it 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. Other uses;
Niobium (Greek mythology: Niobe, daughter of Tantalus) was discovered by Charles Hatchett in 1801. Hatchett found niobium in columbite ore that was sent to England in the 1750s by John Winthrop who was the first governor of Connecticut. There was a considerable amount of confusion about the difference between the closely-related niobium and tantalum that wasn't resolved until 1846 by Heinrich Rose and Charles Marignac who rediscovered the element. Since Rose was unaware of Hatchett's work he gave the element a different name, niobium. In 1864 Christian Blomstrand was the first to prepare the metal. He did this by reducing niobium chloride by heating it in a hydrogen atmosphere.
Columbium was the name originally given to this element by Hatchet but the International Union of Pure and Applied Chemistry (IUPAC) officially adopted "niobium" as the name for element 41 in 1950 after 100 years of controversy. Many leading chemical societies and government organizations refer to it by the official IUPAC name but most leading metallurgists, metal societies, and most leading American commercial producers still refer to the metal by the original "columbium."
The element is never found as a free element but does occur in niobite (Fe, Mn)(Nb, Ta)2)O6]), niobite-tantalite [(Fe, Mn)(Ta, Nb)2)O6], pyrochlore (NaCaNbNb2O6F), and euxenite [(Y, Ca, Ce, U, Th)(Nb, Ta, Ti)2O6]. Minerals that contain niobium often also contain tantalum. Large deposits of niobium have been found associated with carbonatites (carbon-silicate rocks) and as a constituent of pyrochlore. Brazil and Canada are the major producers of niobium mineral concentrates and extensive ore reserves are also in Nigeria, Democratic Republic of Congo, and in Russia.
Naturally occurring niobium is composed of one stable isotope (Nb-93). The most stable radioisotopes are Nb-92 with a half life of 34.7 million years, Nb-94 (half life: 20300 years), and Nb-91 with a half life of 680 years. There is also a meta state at 0.031 mega electron volts whose half life is 16.13 years. Twenty three other radioisotopes have been characterized. Most of these have half lives that are less than two hours except Nb-95 (35 days), Nb-96 (23.4 hours) and Nb-90 (14.6 hours). The primary decay mode before the stable Nb-93 is electron capture and the primary mode after is beta emission with some neutron emission occurring in the first mode of the two mode decay of Nb-104, 109 and 110.
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.