Vanadium

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23 titanium ← vanadium → chromium - ↑ V ↓ Nb Image:V-TableImage.png periodic table
General
Name, Symbol, Number	vanadium, V, 23
Chemical series	transition metals
Group, Period, Block	5, 4, d
Appearance	silvery gray metallic Image:V,23.jpg
Atomic mass	50.9415(1) g/mol
Electron configuration	[Ar] 3d3 4s2
Electrons per shell	2, 8, 11, 2
Physical properties
Phase	solid
Density (near r.t.)	6.0 g/cm³
Liquid density at m.p.	5.5 g/cm³
Melting point	2183 K (1910 °C, 3470 °F)
Boiling point	3680 K (3407 °C, 6165 °F)
Heat of fusion	21.5 kJ/mol
Heat of vaporization	459 kJ/mol
Heat capacity	(25 °C) 24.89 J/(mol·K)
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k at T/K 2101 2289 2523 2814 3187 3679
Atomic properties
Crystal structure	cubic body centered
Oxidation states	5, 3 (amphoteric oxide)
Electronegativity	1.63 (Pauling scale)
Ionization energies (more)	1st: 650.9 kJ/mol
	2nd: 1414 kJ/mol
	3rd: 2830 kJ/mol
Atomic radius	135 pm
Atomic radius (calc.)	171 pm
Covalent radius	125 pm
Miscellaneous
Magnetic ordering	???
Electrical resistivity	(20 °C) 197 nΩ·m
Thermal conductivity	(300 K) 30.7 W/(m·K)
Thermal expansion	(25 °C) 8.4 µm/(m·K)
Speed of sound (thin rod)	(20 °C) 4560 m/s
Young's modulus	128 GPa
Shear modulus	47 GPa
Bulk modulus	160 GPa
Poisson ratio	0.37
Mohs hardness	7.0
Vickers hardness	628 MPa
Brinell hardness	628 MPa
CAS registry number	7440-62-2
Notable isotopes
Main article: Isotopes of vanadium iso NA half-life DM DE (MeV) DP 48V syn 15.97 d ε - 48Ti β+ 0.694 48Ti γ 0.98, 1.3 - 49V syn 330 d ε - 49Ti 50V 0.25% 1.4E17 y ε - 50Ti β- 1.037 50Cr γ 0.78, 1.55 - 51V 99.75% V is stable with 28 neutrons
References

Vanadium is a chemical element in the periodic table that has the symbol V and atomic number 23. A rare, soft and ductile element, vanadium is found combined in certain minerals and is used mainly to produce certain alloys.

Contents 1 Notable characteristics 2 Occurrence 3 Isolation 4 Compounds 5 Isotopes 6 Precautions 7 References 8 External links

Notable characteristics

Vanadium is a soft and ductile, bright white metal. It has good resistance to corrosion by alkalis, sulfuric and hydrochloric acid. It oxidizes readily at about 933 K. Vanadium has good structural strength and a low fission neutron cross section, making it useful in nuclear applications. Although definitely a metal, it shares with Chromium and Manganese the property of having valency oxides with acid properties.

Common oxidation states of vanadium include +2, +3, +4 and +5. A popular experiment with ammonium vanadate (NH₄VO₃), reducing the compound with zinc metal, can demonstrate colorimetrically all four of these vanadium oxidation states. A +1 oxidation state is also rarely seen.

Occurrence

Vanadium is never found unbound in nature but it does occur in about 65 different minerals among which are patronite (VS₄), vanadinite [Pb₅(VO₄)3Cl], and carnotite [K₂(UO₂)₂(VO₄)₂.3H₂O]. Vanadium is also present in bauxite, and in carbon containing deposits such as crude oil, coal, oil shale and tar sands. The spectra of vanadium has also been detected in light from the sun and some other stars.

Much of the vanadium metal being produced is now made by calcium reduction of V₂O₅ in a pressure vessel. Vanadium is usually recovered as a by-product or co-product, and so world resources of the element are not really indicative of available supply.

Isolation

Vanadium is available commercially and production of a sample in the laboratory is not normally required. Commercially, routes leading to metallic vanadium as main product are not usually required as enough is produced as byproduct in other processes.

In industry, heating of vanadium ore or residues from other processes with salt, NaCl, or sodium carbonate, Na₂CO₃, at about 850°C gives sodium vanadate, NaVO₃. This is dissolved in water and acidified to give a red solid which in turn is melted to form a crude form of vanadium pentoxide, "V₂O₅". Reduction of vanadium pentoxide with calcium, Ca, gives pure vanadium. An alternative suitable for small scales is the reduction of vanadium pentachloride, VCl₅, with hydrogen, H₂, or magnesium, Mg. Many other methods are also in use.

Industrially, most vanadium is used as an additive to improve steels. Rather than proceed via pure vanadium metal it is often sufficient to react the crude of vanadium pentoxide, "V₂O₅", with crude iron. This produces ferrovanadium suitable for further work

Compounds

Vanadium pentoxide (V₂O₅) is used as a catalyst, dye and color-fixer. It is extremely toxic if inhaled, and dangerous for the environment.

Vanadyl sulfate (VOSO₄), also called vanadium(IV) sulfate oxide hydrate, is used as a relatively controversial dietary supplement, primarily for increasing insulin levels and body-building. Whether it works for the latter purpose has not been proven, and there is some evidence that athletes who take it are merely experiencing a placebo effect. It is toxic in high doses.

Isotopes

Naturally occurring vanadium is composed of 1 stable isotope; V-51. 15 radioisotopes have been characterized with the most stable being V-50 with a half-life of 1.4E17 years, V-49 with a half-life of 330 days, and V-48 with a half-life of 15.9735 days. All of the remaining radioactive isotopes have half-lifes that are less than 1 hour and the majority of these have half lifes that are less than 10 seconds. This element also has 1 meta state.

The isotopes of vanadium range in atomic weight from 43.981 amu (V-43) to 59.959 amu (V-59). The primary decay mode before the most abundant stable isotope, V-51, is electron capture and the primary mode after is beta decay. The primary decay products before V-51 are element 22 (titanium) isotopes and the primary products after are element 24 (chromium) isotopes.

Precautions

Powdered metallic vanadium is a fire hazard, and unless known otherwise, all vanadium compounds should be considered highly toxic. Generally, the higher the oxidation state of vanadium, the more toxic the compound is. The most dangerous one is vanadium pentoxide. Vanadium compounds may cause lung cancer if inhaled.

The Occupational Safety and Health Administration (OSHA) has set an exposure limit of 0.05 mg/m³ for vanadium pentoxide dust and 0.1 mg/m³ for vanadium pentoxide fumes in workplace air for an 8-hour workday, 40-hour work week.

The National Institute for Occupational Safety and Health (NIOSH) has recommended that 35 mg/m³ of vanadium be considered immediately dangerous to life and health. This is the exposure level of a chemical that is likely to cause permanent health problems or death.

References

• Los Alamos National Laboratory – Vanadium

External links

• WebElements.com – Vanadium
• Mineral Information Institute – Vanadium
• ATSDR – ToxFAQs: Vanadium
• The Vanadium Redox Battery was invented at The University of New South Wales