Vanadium

Vanadium, ₂₃V
General properties
Pronunciation	/vəˈneɪdiəm/ (və-NAY-dee-əm)
Appearance	blue-silver-grey metal
Standard atomic weight (Ar, standard)	50.9415(1)
Vanadium in the periodic table
	titanium ← vanadium → chromium
Atomic number (Z)	23
Group	group 5
Period	period 4
Element category	transition metal
Block	d-block
Electron configuration	[Ar] 3d3 4s2
Electrons per shell	2, 8, 11, 2
Physical properties
Phase at STP	solid
Melting point	2183 K (1910 °C, 3470 °F)
Boiling point	3680 K (3407 °C, 6165 °F)
Density (near r.t.)	6.0 g/cm3
when liquid (at m.p.)	5.5 g/cm3
Heat of fusion	21.5 kJ/mol
Heat of vaporization	444 kJ/mol
Molar heat capacity	24.89 J/(mol·K)
Atomic properties
Oxidation states	5, 4, 3, 2, 1, −1, −3 (an amphoteric oxide)
Electronegativity	Pauling scale: 1.63
Ionization energies	1st: 650.9 kJ/mol; 2nd: 1414 kJ/mol; 3rd: 2830 kJ/mol; (more);
Atomic radius	empirical: 134 pm
Covalent radius	153±8 pm
	Spectral lines
	Spectral lines
Miscellanea
Crystal structure	body-centered cubic (bcc)
Speed of sound thin rod	4560 m/s (at 20 °C)
Thermal expansion	8.4 µm/(m·K) (at 25 °C)
Thermal conductivity	30.7 W/(m·K)
Electrical resistivity	197 nΩ·m (at 20 °C)
Magnetic ordering	paramagnetic
Magnetic susceptibility	+255.0·10−6 cm3/mol (298 K)
Young's modulus	128 GPa
Shear modulus	47 GPa
Bulk modulus	160 GPa
Poisson ratio	0.37
Mohs hardness	6.7
Vickers hardness	628–640 MPa
Brinell hardness	600–742 MPa
CAS Number	7440-62-2
History
Discovery	Andrés Manuel del Río (1801)
First isolation	Nils Gabriel Sefström (1830)
Named by	Nils Gabriel Sefström (1830)
Main isotopes of vanadium
β−	50Cr
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Vanadium is a chemical element with symbol V and atomic number 23. It is a hard, silvery grey, ductile, and malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer (passivation) stabilizes the free metal somewhat against further oxidation.

Andrés Manuel del Río discovered compounds of vanadium in 1801 in Mexico by analyzing a new lead-bearing mineral he called "brown lead", and presumed its qualities were due to the presence of a new element, which he named erythronium (derived from Greek for "red") since, upon heating, most of the salts turned red. Four years later, however, he was (erroneously) convinced by other scientists that erythronium was identical to chromium. Chlorides of vanadium were generated in 1830 by Nils Gabriel Sefström who thereby proved that a new element was involved, which he named "vanadium" after the Scandinavian goddess of beauty and fertility, Vanadís (Freyja). Both names were attributed to the wide range of colors found in vanadium compounds. Del Rio's lead mineral was later renamed vanadinite for its vanadium content. In 1867 Henry Enfield Roscoe obtained the pure element.

Vanadium occurs naturally in about 65 different minerals and in fossil fuel deposits. It is produced in China and Russia from steel smelter slag; other countries produce it either from the flue dust of heavy oil, or as a byproduct of uranium mining. It is mainly used to produce specialty steel alloys such as high-speed tool steels. The most important industrial vanadium compound, vanadium pentoxide, is used as a catalyst for the production of sulfuric acid.

Large amounts of vanadium ions are found in a few organisms, possibly as a toxin. The oxide and some other salts of vanadium have moderate toxicity. Particularly in the ocean, vanadium is used by some life forms as an active center of enzymes, such as the vanadium bromoperoxidase of some ocean algae.