Vanadium Element in Periodic Table
Vanadium (V), chemical element, shining silvery-white, low-density transition metal of Group 5 (VIB) of the periodic table widely used for alloy making. The pure vanadium metal is soft, malleable properties, and ductile but impurities make it hard and brittle. The metal alloyed with steel and iron uses for making springs and high-speed tools.
The white shining cubic crystal lattice, vanadium has chemical symbol V, atomic number 23, atomic weight 50.94, melting point 1910 °C, boiling point 3407 °C, and valence shell electron configuration [Ar] 3d3 4s2. The melting point and density of vanadium higher than those of titanium suggest that the greater involvement of d-electron in metallic chemical bonding. It has the highest melting point in the first transition series with a stable +5 oxidation number or state which is not strongly oxidized.
History and Occurrence of Vanadium
The presence of a new element in some Mexican lead ore was first discovered by Spanish mineralogist Andres Manuel del Rio in 1801, who named it erythronium from the Greek latter erythos meaning red. In 1830 Swedish chemist Nils Gabriel Sefström found the same element in the Swedish iron ore which produced different types of compounds with a variety of beautiful colors. Therefore, he named the chemical element vanadium according to the Scandinavian Goddess of beauty, Vanadis. The English chemist Henry Enfield Roscoe in 1831 first isolated the metal by hydrogen reduction of vanadium chloride (VCl2). In 1925, the American chemist John Wesley Marden and Malcolm N. Rich prepared the pure form of the metal (99.7 percent) by the reduction of vanadium pentoxide (V2O5) with calcium.
Vanadium is the fifth most abundant transition metal and the twentieth most abundant element among all periodic table elements. It presents 0.0136 percent of the earth’s crustal rocks. Various minerals (carnotite, vanadinite, roscoelite), coal, and crude petroleum oils are the main source of vanadium, occurs commercially in different countries like Venezuelan, Mexico. China, South Africa, and Russia. Some mineral water springs and certain invertebrates and plants have a high concentration of vanadium in their body.
Extraction of Element
Vanadium is obtained as a by-product in the production of uranium from carnotite. Crushed and concentrated ore is roasted in air and leached with sodium carbonate solution to produce sodium uranyl carbonate and sodium vanadate. The mixed compounds pass into the filtrate for separation. The filtrate containing sodium vanadate is treated with ammonia or ammonium chloride to precipitate orange ammonium vanadate (NaVO3 + NH4Cl → NH4VO3 + NaCl). Alternatively, the sodium vanadate solution was acidified with dilute sulfuric acid (pH scale 2 to 3) to precipitate polyvanadate. The ammonium vanadate is ignited to produce black pentoxide (V2O5), black color due to the presence of impurities. The oxide mostly (90 percent) used to make ferrovanadium steel. Metallic vanadium may be obtained from the oxide by reduction with hot calcium in an inert atmosphere.
The metal purified by conversion to VCl4 followed by reduction with magnesium or a very pure form of vanadium obtained by pyrolysis VI3 (van Arkel process). Most of the commercial-grade vanadium pentoxide (V2O5) is converted to ferrovanadium, an alloy containing 50 percent iron.
Vanadium has a total of five electrons in valence orbitals and shows all the oxidation states +1 to +5, among these +2 and +5 states are stable and important in chemistry. The aqueous chemistry is characterized by polymeric species commonly known as isopolyvandates. V (IV) is most stable under normal conditions, represented by the halides and vanadyl ion (VO+2). V (II) is a milder reducing agent than Ti (III) and stable in an aqueous solution. In the +1 oxidation state, it is strongly reducing in nature and rapidly oxidized in air and water.
Vanadium pentoxide (V2O5) is a commercially important chemical catalyst uses for the production of sulfuric acid and electrodes in redox battery. The lower oxides are obtained by heating metal with excess oxygen. The pure vanadium oxide is an orange crystalline solid (melting point 670 °C) but the technical variety is brown.
Halides and Oxohalides
In learning chemistry, the halide of vanadium contains the chemical formula VXn (where X = halides), but VI4, VCl5, VBr5, and VI5 are extremely unstable of do not exist. VF5 is the only pentahalide in the +5 state prepared by heating the metal with fluorine at 300 °C or disproportionation of VF4. It is a violent oxidizing and fluorinating agent. Three tetrahalides of vanadium in +4 state prepared by direct reaction of metal with fluorine, chlorine, or bromine, act as a Lewis acids adduct by bases like SeF4, NH3, and pyridine. In +2 and +3 states all the di or tetra halides are stable at room temperature.
Vanadium form any oxohalides having the chemical formula VOmXn. The oxy trifluoride may be prepared by reacting VF5 with air. VOCl3 and VOBr3 are the most common and important oxides of metal obtained by the action of Cl2 or Br2 on V2O5 or a mixture of V2O5 and carbon.
In organometallic chemistry, vanadium forms sandwich-type complexes with cyclopentadiene and benzene. Vanadocene is a paramagnetic violet-black solid largely applied in organic chemistry. When VCl3, 3THF is treated with a large excess of lithium phenyl in ether, the purple complex Li4VPh6, 3.5 Et2O is obtained.
Uses of Vanadium
Vanadium is largely used in making alloy steel for making industrial springs and high-speed tools like aerospace and defense industries. Even a small percentage (0.1 to 0.3 percent) of vanadium metal combines with carbon present in the steel to form finely dispersed carbides like V4C3 which increases the mechanical strength of the alloy at high temperature. Chrome vanadium steel is very suitable for making shafts, axles, and motor car frame. Useful alloys are formed with other metals like copper, nickel, aluminum, etc. In nuclear power plant, vanadium or its compounds is a suitable material to construct the structure of the nuclear fusion reactor.
Vanadium is a good scavenger in metallurgical operations to remove the last traces of oxygen molecules. Vanadium and its oxide compounds are widely used as a chemical catalyst in organic and inorganic chemistry, for the oxidation of naphthalene to phthalic acid, toluene to benzaldehyde, hydrogenation of alkene or olefins and aromatic hydrocarbon.