   #copyright

Vanadium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


                23             titanium ← vanadium → chromium
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                V
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                Nb

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                      Name, Symbol, Number vanadium, V, 23
                                         Chemical series transition metals
                                              Group, Period, Block 5, 4, d
                                              Appearance silver-grey metal
                                             Atomic mass 50.9415 (1) g/mol
                                     Electron configuration [Ar] 3d^3 4s^2
                                           Electrons per shell 2, 8, 11, 2
                                                       Physical properties
                                                               Phase solid
                                        Density (near r.t.) 6.0 g·cm^−3
                                     Liquid density at m.p. 5.5 g·cm^−3
                                                     Melting point 2183  K
                                                    (1910 ° C, 3470 ° F)
                                                      Boiling point 3680 K
                                                    (3407 ° C, 6165 ° F)
                                          Heat of fusion 21.5 kJ·mol^−1
                                     Heat of vaporization 459 kJ·mol^−1
                          Heat capacity (25 °C) 24.89 J·mol^−1·K^−1

   CAPTION: 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 2, 3, 4, 5
                                                       ( amphoteric oxide)
                                    Electronegativity 1.63 (Pauling scale)
                                                       Ionization energies
                                           ( more) 1st: 650.9 kJ·mol^−1
                                                    2nd: 1414 kJ·mol^−1
                                                    3rd: 2830 kJ·mol^−1
                                                      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^−1·K^−1
                        Thermal expansion (25 °C) 8.4 µm·m^−1·K^−1
                               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
                                                         Selected isotopes

                 CAPTION: Main article: Isotopes of vanadium

                            iso    NA    half-life    DM   DE ( MeV)  DP
                            ^48V syn    15.9735 d   ε+ β^+ 4.0123    ^48Ti
                            ^49V syn    330 d       ε      0.6019    ^49Ti
                            ^50V 0.25%  1.5×10^17 y ε      2.2083    ^50Ti
                                                    β^-    1.0369    ^50Cr
                            ^51V 99.75% V is stable with 28 neutrons

                                                                References

   Vanadium ( IPA: /vəˈneɪdiəm/) 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. It is one of the 26 elements
   commonly found in living things.

Notable characteristics

   Vanadium is a soft and ductile, silver-grey 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 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 NH[4]VO[3], reducing the
   compound with zinc metal, can demonstrate colorimetrically all four of
   these vanadium oxidation states. A +1 oxidation state is rarely seen.

Applications

   Approximately 80% of vanadium produced is used as ferrovanadium or as a
   steel additive. Other uses:
     * In such alloys as:
          + specialty stainless steel, e.g. for use in surgical
            instruments and tools.
          + rust resistant and high speed tool steels.
          + mixed with aluminium in titanium alloys used in jet engines
            and high-speed airframes
     * Vanadium steel alloys are used in axles, crankshafts, gears, and
       other critical components.
     * It is an important carbide stabilizer in making steels.
     * Because of its low fission neutron cross section, vanadium has
       nuclear applications.
     * Vanadium foil is used in cladding titanium to steel.
     * Vanadium-gallium tape is used in superconducting magnets (175,000
       gauss).
     * Vanadium pentoxide V[2]O[5] is used as a catalyst in manufacturing
       sulfuric acid (via the contact process) and maleic anhydride. It is
       also used in making ceramics.
     * Glass coated with vanadium dioxide VO[2] can block infrared
       radiation (and not visible light) at a specific temperature.
     * Electrical fuel cells and storage batteries such as vanadium redox
       batteries.
     * Added to corundum to make simulated Alexandrite jewelry.
     * Vanadate electrochemical conversion coatings for protecting steel
       against rust and corrosion

History

   Vanadium was originally discovered by Andrés Manuel del Río (a Spanish
   mineralogist) in Mexico City, in 1801. He called it "brown lead" (now
   named vanadinite). Through experimentation, its colors reminded him of
   chromium, so he named the element panchromium. He later renamed this
   compound erythronium, since most of the salts turned red when heated.
   The French chemist Hippolyte Victor Collet-Descotils incorrectly
   declared that del Rio's new element was only impure chromium. Del Rio
   thought himself to be mistaken and accepted the statement of the French
   chemist that was also backed by Del Rio's friend Baron Alexander von
   Humboldt.

   In 1831, Sefström of Sweden rediscovered vanadium in a new oxide he
   found while working with some iron ores and later that same year
   Friedrich Wöhler confirmed del Rio's earlier work. Later, George
   William Featherstonhaugh, one of the first US geologists, suggested
   that the element should be named "rionium" after Del Rio, but this
   never happened.

   Metallic vanadium was isolated by Henry Enfield Roscoe in 1867, who
   reduced vanadium(III) chloride VCl[3] with hydrogen. The name vanadium
   comes from Vanadis, a goddess in Scandinavian mythology, because the
   element has beautiful multicolored chemical compounds.

Biological role

   In biology, a vanadium atom is an essential component of some enzymes,
   particularly the vanadium nitrogenase used by some nitrogen-fixing
   micro-organisms. Vanadium is essential to ascidians or sea squirts in
   vanadium chromagen proteins. The concentration of vanadium in their
   blood is more than 100 times higher than the concentration of vanadium
   in the seawater around them. Rats and chickens are also known to
   require vanadium in very small amounts and deficiencies result in
   reduced growth and impaired reproduction.

   Administration of oxovanadium compounds has been shown to alleviate
   diabetes mellitus symptoms in certain animal models and humans. Much
   like the chromium effect on sugar metabolism, the mechanism of this
   effect is unknown.

Mineral supplement in drinking water

   Vanadium pentoxide V[2]O[5] is marketed in Japan as a good mineral
   health supplement naturally occurring in drinking water. The source of
   this drinking water is mainly the slopes of Mount Fuji. The water's
   vanadium pentoxide content ranges from about 80 to 130 μg/liter. It is
   marketed as being effective against diabetes, eczema, and obesity.
   There is no mention of its toxicity in the marketing of these products.

Occurrence

   Vanadium is never found unbound in nature but it does occur in about 65
   different minerals among which are patronite VS[4], vanadinite
   Pb[5](VO[4])[3]Cl, and carnotite K[2](UO[2])[2](VO[4])[2].3H[2]O.
   Vanadium is also present in bauxite, and in carbon containing deposits
   such as crude oil, coal, oil shale and tar sands. Vanadium has also
   been detected spectroscopically in light from the Sun and some other
   stars.

   Much of the vanadium metal being produced is now made by calcium
   reduction of V[2]O[5] 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 Na[2]CO[3] at about 850°C gives
   sodium vanadate NaVO[3]. 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 V[2]O[5]. Reduction of vanadium pentoxide with
   calcium gives pure vanadium. An alternative suitable for small scales
   is the reduction of vanadium pentachloride VCl[5] with hydrogen or
   magnesium. 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 V[2]O[5] with crude iron. This
   produces ferrovanadium suitable for further work.

Compounds

   Vanadium pentoxide V[2]O[5] is used as a catalyst principally in the
   production of sulfuric acid. It is the source of vanadium used in the
   manufacture of ferrovanadium. It can be used as a dye and colour-fixer.

   Vanadyl sulfate VOSO[4], 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.

   Vanadium(IV) chloride VCl[4] is a soluble form of vanadium that is
   commonly used in the laboratory. V(IV) is the reduced form of V(V), and
   commonly occurs after anaerobic respiration by dissimilatory metal
   reducing bacteria. VCl[4] reacts violently with water.

Toxicity of vanadium compounds

   The toxicity of vanadium depends on its physico-chemical state;
   particularly on its valence state and solubility. Pentavalent VOSO[4]
   has been reported to be more than 5 times as toxic as trivalent
   V[2]O[3](Roschin, 1967). Vanadium compounds are poorly absorbed through
   the gastrointestinal system. Inhalation exposures to vanadium and
   vanadium compounds result primarily in adverse effects to the
   respiratory system (Sax, 1984; ATSDR, 1990). Quantitative data are,
   however, insufficient to derive a subchronic or chronic inhalation.

   There is little evidence that vanadium or vanadium compounds are
   reproductive toxins or teratogens. There is also no evidence that any
   vanadium compound is carcinogenic; however, very few adequate studies
   are available for evaluation. Vanadium has not been classified as to
   carcinogenicity by the U.S. EPA (1991a).

Isotopes

   Naturally occurring vanadium is composed of one stable isotope ^51V and
   one radioactive isotope ^50V with a half-life of 1.5×10^17 years. 24
   artificial radioisotopes have been characterized (in the range of mass
   number between 40 and 65) with the most stable being ^49V with a
   half-life of 330 days, and ^48V with a half-life of 15.9735 days. All
   of the remaining radioactive isotopes have half-lives shorter than an
   hour, the majority of them below 10 seconds. In 4 isotopes, metastable
   excited states were found (including 2 metastable states for ^60V).

   The primary decay mode before the most abundant stable isotope ^51V is
   electron capture. The next most common mode is beta decay. The primary
   decay products before ^51V 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.

   The Occupational Safety and Health Administration (OSHA) has set an
   exposure limit of 0.05 mg/m^3 for vanadium pentoxide dust and 0.1
   mg/m^3 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/m^3 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.
   Retrieved from " http://en.wikipedia.org/wiki/Vanadium"
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   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
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