Niobium

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Niobium,  41Nb
General properties
Name, symbol Niobium, Nb
Appearance Silvery gray metallic
Bluish (oxidized)
Niobium in the periodic table
V

Nb

Ta
ZirconiumNiobiumMolybdenum
Atomic number 41
Standard atomic weight (Ar) 92.90637(2)
Group, block 5; d-block
Period period 5
Electron configuration [Kr] 4d4 5s1
per shell
2, 8, 18, 12, 1
Physical properties
Silvery metallic
Phase Solid
Melting point 2750 K ​(2477 °C, ​​4491 °F)
Boiling point 5017 K ​(4744 °C, ​​8571 °F)
Density near r.t. 8.57 g/cm3
Heat of fusion 30 kJ/mol
Heat of 689.9 kJ/mol
Molar heat capacity 24.60 J/(mol·K)
 pressure
Atomic properties
Oxidation states 5, 4, 3, 2, 1, −1, −3 ​(a mildly acidic oxide)
Electronegativity Pauling scale: 1.6
energies 1st: 652.1 kJ/mol
2nd: 1380 kJ/mol
3rd: 2416 kJ/mol
Atomic radius empirical: 146 pm
Covalent radius 164±6 pm
Miscellanea
Crystal structure ​body-centered cubic (bcc)
Speed of sound thin rod 3480 m/s (at 20 °C)
Thermal expansion 7.3 µm/(m·K)
Thermal conductivity 53.7 W/(m·K)
Electrical resistivity 152 Ω·m
Magnetic ordering Paramagnetic
Young's modulus 105 GPa
Shear modulus 38 GPa
Bulk modulus 170 GPa
Poisson ratio 0.40
Mohs hardness 6.0
Vickers hardness 870–1320 MPa
Brinell hardness 735–2450 MPa
CAS Registry Number 7440-03-1
History
Naming after Niobe in Greek mythology, daughter of Tantalus
Discovery Charles Hatchett (1801)
First isolation Christian Wilhelm Blomstrand (1864)
· references

Niobium is a chemical element with symbol Nb and atomic number 41. It was formerly known as columbium (Cb), before its name was changed in 1949.

Properties

Chemical

Niobium is highly resistant to corrosion. At room temperature is only attacked by hydrofluoric acid, but hot minerals acids will corrode it. It also reacts with fluorine at room temperature. At higher temperatures it reacts with chlorine and hydrogen, at 200 °C, while at 400 °C niobium reacts with nitrogen. Niobium is resistant to fused alkalis.

Physical

Niobium is a lustrous, grey, ductile, transition metal when pure, but becomes brittle if impurities are present. In the presence of air, the surface of the metal develops a protective oxide coating, giving the metal a blueish color.

Niobium becomes a superconductor at cryogenic temperatures, and has the highest critical temperature of the elemental superconductors, 9.2 K. The superconductive properties are strongly dependent on the purity of the niobium metal. It is also one of the three elemental Type II superconductors, along with vanadium and technetium. Niobium has the largest magnetic penetration depth of any element.

Availability

Niobium is sold by various chemical suppliers and other metal companies.

Isolation

Niobium can be obtained by reducing niobium pentoxide with a reducing agent, such as carbon, hydrogen. Another way involves the aluminothermic reaction a mixture of niobium pentoxide, iron(III) oxide and aluminium:

3 Nb2O5 + Fe2O3 + 12 Al → 6 Nb + 2 Fe + 6 Al2O3

Oxidizers like sodium nitrate can be added to speed up the reaction. The resulting ferroniobium can be further purified.

Projects

  • Make lithium niobate
  • Make superalloys

Handling

Safety

Niobium has no known biological role, however elemental niobium on a larger scale is physiologically inert (and thus hypoallergenic) and harmless, being used in jewelry and in some medical implants. Niobium dust is an eye and skin irritant and a potential fire hazard.

Niobium halides hydrolyze in the presence of moisture and thus will cause burns to the skin.

Storage

Niobium can be stored in any container.

Disposal

Niobium doesn't require special disposal. Its compounds can be converted to niobium oxide, which is harmless.

References

Relevant Sciencemadness threads