41
  Nb  
92.906380
Niobium

Name: Niobium
Symbol: Nb
Atomic Number: 41
AtomicWeight: 92.906380
Family: Transition Metals
CAS RN: 7440-03-1
Description: A shiny, white, soft, and ductile metal.
State (25 C): Solid
Oxidation states: +3, +5

Molar Volume: 10.84 cm3/mole
Valence Electrons: 4d45s1

Boiling Point:  5017K, 4744C, 8571F
Melting Point:
2741K, 2468C, 4474F
Electrons Energy Level: 2, 8, 18, 12, 1
Isotopes: 32 + 1 Stable
Heat of Vaporization: 682 kJ/mol
Heat of Fusion: 26.4 kJ/mol
Density: 8.57 g/cm3 @ 300K
Specific Heat: 0.26 J/gK
Atomic Radius: 2.08
Ionic Radius: 0.69
Electronegativity: 1.6 (Pauling); 1.23 (Allrod Rochow)
Vapor Pressure: 0.0755 Pa @ 2468C

1s2 2s2p6 3s2p6d10 4s2p6d4 5s1

History

Niobium (Greek mythology: Niobe, daughter of Tantalus).   The first governor of Connecticut, John Winthrop the Younger, discovered a new mineral around 1734.  He named the mineral columbite ((Fe, Mn, Mg)(Nb, Ta)2O6) and sent a sample of it to the British Museum in London, England.  The columbite sat in the museum's mineral collection for years until it was found and analyzed by Charles Hatchett in 1801.  Hatchett could tell that there was an unknown element in the columbite, but he was not able to isolate it.  He named the new element columbium.

The fate of columbium took a drastic turn in 1809 when William Hyde Wollaston, an English chemist and physicist, compared the minerals columbite and tantalite ((Fe, Mn)(Ta, Nb)2O6) and declared that columbium was actually the element tantalum.  This confusion arose because tantalum and niobium are similar metals, are always found together and are very difficult to isolate.

Niobium was rediscovered and renamed by Heinrich Rose in 1844 when he produced two new acids, niobic acid and pelopic acid, from samples of columbite and tantalite.  These acids are very similar to each other and it took another twenty-two years and a Swiss chemist named Jean Charles Galissard de Marignac to prove that these were two distinct chemicals produced from two different elements.  Metallic niobium was finally isolated by the Swedish chemist Christian Wilhelm Blomstrand in 1864 by reducing niobium chloride by heating it in a hydrogen atmosphere.  Today, niobium is primarily obtained from the minerals columbite and pyrochlore ((Ca, Na)2Nb2O6(O, OH, F)).

Columbium (symbol Cb) was the name originally given to this element by Hatchett, 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. This was a compromise of sorts; the IUPAC accepted tungsten instead of wolfram, in deference to North American usage; and niobium instead of columbium, in deference to European usage. Not everyone agreed, however, and while many leading chemical societies and government organizations refer to it by the official IUPAC name, many leading metallurgists, metal societies, and most leading American commercial producers still refer to the metal by the original "columbium".

Characteristics

A rare, soft,  shiny gray, ductile transition metal that takes on a bluish tinge when exposed to air at room temperature for extended periods.  Niobium is found in niobite and used in alloys.   The most notable alloys are used to make special steels and strong welded joints.   Niobium was discovered in a variety of columbite (now called niobite) and was at first named after this mineral.

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d4
5s1

When it is processed at even moderate temperatures niobium must be placed in a protective atmosphere.  The metal begins to oxidize in air at 200C; its most common oxidations states are +3, and +5, although others are also known.

Occurrence

The element is never found as a free element but does occur in the minerals columbite ((Fe, Mn)(Nb, Ta)2O6), columbite-tantalite or coltan ((Fe,Mn)(Ta,Nb)2O6), pyrochlore ((Na, Ca)2Nb2O6OH, F), 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 igneous 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.  A large producer in Brazil is CBMM located in Araxa, Minas Gerais.

Applications

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;

Pure niobium is itself a superconductor when it is cooled to cryogenic temperatues below 9.25 K (-442.75F).  At atmospheric pressure, it has the highest critical temperature of the elemental superconductors: 9.3oK.   Niobium has the largest magnetic penetration depth of any element.  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.  Niobium is also used in its pure form to make superconducting accelerating structures for particle accelerators.

Superconductive niobium cavities are at the heart of a machine built at the Thomas Jefferson National Accelerator Facility.  This machine, called an electron accelerator, is used by scientists to study the quark structure of matter.  The accelerator's 338 niobium cavities are bathed in liquid helium and accelerted electrons to nearly the speed of light.

Compounds

Niobium Ore
Columbite, (Fe, Mn)(Nb, Ta)2O6
Columbite-Tantalite or Coltan, (Fe,Mn)(Ta,Nb)2O6
Pyrochlore, (Na, Ca)2Nb2O6OH, F
Euxenite, (Y, Ca, Ce, U, Th)(Nb,Ta,, Ti)2O6

Isotopes

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: 20,300 years), and Nb-91 with a half life of 680 years. There is also a meta state at 0.031 megaelectronvolts whose half-life is 16.13 years.  Thirty two 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. It is worth 4 dollars a gram. Charles Hatchett could not isolate the elements tantalum and columbium (niobium). Christian Blomstrand could separate them, however.

atom.gif (700 bytes)

Isotope  
Atomic Mass
 
Half-Life
81Nb 80.94903 <44 ns
82Nb 81.94313 51 ms
83Nb 82.93671 4.1 seconds
84Nb 83.93357 9.8 seconds
85Nb 84.92791 20.9 seconds
86Nb 85.92504 88 seconds
87Nb 86.92036 3.75 minutes
88Nb 87.91833 14.55 minutes
89Nb 88.913418 2.03 hours
90Nb 89.911265 14.60 hours
91Nb 90.906996 680 years
92Nb 91.907194 3.47E 7 years
93Nb 92.9063781(26) Stable
94Nb 93.9072839 20,300 years
95Nb 94.9068358 34.991 days
96Nb 95.908101 23.35 hours
97Nb 96.9080986 72.1 minutes
98Nb 97.910328 2.86 seconds
99Nb 98.911618 15.0 seconds
100Nb 99.914182 1.5 seconds
101Nb 100.915252 7.1 seconds
102Nb 101.91804 1.3 seconds
103Nb 102.91914 1.5 seconds
104Nb 103.92246 4.9 seconds
105Nb 104.92394 2.95 seconds
106Nb 105.92797 920 ms
107Nb 106.93031 300 ms
108Nb 107.93484 0.193 seconds
109Nb 108.93763 190 ms
110Nb 109.94244 170 ms
111Nb 110.94565 >300 ns
112Nb 111.95083 >300 ns
113Nb 112.95470 >300 ns

Precautions

40px-Skull_and_crossbones.svg.jpg (1420 bytes) 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 known biological role. However, people use niobium for colored body jewelry.

atom.gif (700 bytes)

Niobium Data
 

Atomic Structure

  • Atomic Radius: 2.08
  • Atomic Volume: 10.87cm3/mol
  • Covalent Radius: 1.34
  • Cross Section (Thermal Neutron Capture) Barns: 1.15
  • Crystal Structure: Cubic body centered
  • Electron Configuration:
    1s2 2s2p6 3s2p6d10 4s2p6d4 5s1
  • Electrons per Energy Level: 2, 8, 18, 12, 1
  • Ionic Radius: 0.69
  • Filling Orbital: 4d4
  • Number of Electrons (with no charge): 41
  • Number of Neutrons (most common/stable nuclide): 52
  • Number of Protons: 41
  • Oxidation States: 5,3
  • Valence Electrons: 4d4 5s1

Chemical Properties

  • Electrochemical Equivalent: 0.69327 g/amp-hr
  • Electron Work Function: 4.3eV
  • Electronegativity: 1.6 (Pauling); 1.23 (Allrod Rochow)
  • Heat of Fusion: 26.4 kJ/mol
  • Incompatibilities:
  • Ionization Potential
    • First: 6.88
    • Second: 14.32
    • Third: 25.04
  • Valence Electron Potential (-eV): 104

Physical Properties

  • Atomic Mass Average: 92.90638
  • Boiling Point: 5017K, 4744C, 8571F
  • Coefficient of Lineal Thermal Expansion: /K-1: 7.07E-6
  • Conductivity
    Electrical: 0.0693 106/cm
    Thermal: 0.537 W/cmK
  • Density: 8.57 g/cm3 @ 300K
  • Description:
    Shiny white soft transition metal. Niobium resists corrosion due to an oxide film on its surface.
  • Elastic Modulus:
    • Bulk: 170.3/GPa
    • Rigidity: 37.5/GPa
    • Youngs: 104.9/GPa
  • Enthalpy of Atomization: 745 kJ/mole @ 25C
  • Enthalpy of Fusion: 27.2 kJ/mole
  • Enthalpy of Vaporization: 696.6 kJ/mole
  • Flammablity Class:
  • Freezing Point: see melting point
  • Hardness Scale
    • Brinell: 736 MN m-2
    • Mohs: 6
    • Vickers: 1320 MN m-2
  • Heat of Vaporization: 682 kJ/mol
  • Melting Point: 2741K, 2468C, 4474F
  • Molar Volume: 10.84 cm3/mole
  • Physical State (at 20C & 1atm): Solid
  • Specific Heat: 0.26 J/gK
  • Vapor Pressure: 0.0755 Pa @ 2468C

Regulatory / Health

  • CAS Number
    • 7440-03-1
  • OSHA Permissible Exposure Limit (PEL)
    • No limits set by OSHA
  • OSHA PEL Vacated 1989
    • No limits set by OSHA
  • NIOSH Recommended Exposure Limit (REL)
    • No limits set by NIOSH
  • Levels In Humans:
    Note: this data represents naturally occuring levels of elements in the typical human, it DOES NOT represent recommended daily allowances.
    • Blood/mg dm-3: 0.005
    • Bone/p.p.m: <0.07
    • Liver/p.p.m: 0.14
    • Muscle/p.p.m: 0.14
    • Daily Dietary Intake: 0.02-06 mg
    • Total Mass In Avg. 70kg human: 1.5 mg
  • Discovery Year: 1801
  • Name Origin:
    From Niobe; daughter of the mythical Greek king Tantalus.
  • Abundance:
    • Earth's Crust/p.p.m.: 20
    • Seawater/p.p.m.: 0.0000009
    • Atmosphere/p.p.m.: N/A
    • Sun (Relative to H=1E12): 79
  • Sources:
    Found in columbite, samarskite and betafite ores. Also obtained as a by-product of tin-extraction. Annual world wide production is around 15,000 tons. Primary mining areas are Australia, Zaire, Brazil, Russia, Norway, Canada and Madagascar.
  • Uses:
    It is used in stainless steel alloys for nuclear reactors, jets, missiles, cutting tools, pipelines, super magnets and welding rods.

Ionization Energy (eV): 6.759 eV
Estimated Crustal Abundance: 2.0101 milligrams per kilogram
Estimated Oceanic Abundance:
110-5 milligrams per liter

Transition Metals
Group 3
(IIIB)
4
(IVB)
5
(VB)
6
(VIB)
7
(VIIB)
8
(VIIIB)
9
(VIIIB)
10 (VIIIB) 11
(IB)
12
(IIB)
Period 4 21
Sc
44.95
22
Ti
47.86
23
V
50.94
24
Cr
51.99
25
Mn
54.93
26
Fe
55.84
27
Co
58.93
28
Ni
58.69
29
Cu
63.54
30
Zn
65.39
Period 5 39
Y
88.90
40
Zr
91.22
41
Nb
92.90
42
Mo
95.94
43
Tc
98.00
44
Ru
101.0
45
Rh
102.9
46
Pd
106.4
47
Ag
107.8
48
Cd
112.4
Period 6 57
La
138.9
72
Hf
178.4
73
Ta
180.9
74
W
183.8
75
Re
186.2
76
Os
190.2
77
Ir
192.2
78
Pt
195.0
79
Au
196.9
80
Hg
200.5
Period 7 89
Ac
227.0
104
Rf
261.0
105
Db
262.0
106
Sg
266.0
107
Bh
264.0
108
Hs
269.0
109
Mt
268.0
110
Ds
269.0
111
Rg
272.0
112
Uub
277.0