|Pronunciation|| / /|
|Standard atomic weight Ar, std(V)||50.9415(1)|
|Vanadium in the periodic table|
|Atomic number (Z)||23|
|Electron configuration||[ Ar ] 3d3 4s2|
|Electrons per shell||2, 8, 11, 2|
|Phase at STP||solid|
|Melting point||2183 K (1910 °C,3470 °F)|
|Boiling point||3680 K(3407 °C,6165 °F)|
|Density (near r.t.)||6.11 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)|
| Vapor pressure |
|Oxidation states||−3, −1, 0, +1, +2, +3, +4, +5 (an amphoteric oxide)|
|Electronegativity||Pauling scale: 1.63|
|Atomic radius||empirical:134 pm|
|Covalent radius||153±8 pm|
|Spectral lines of vanadium|
|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)|
|Molar magnetic susceptibility||+255.0×10−6 cm3/mol(298 K)|
|Young's modulus||128 GPa|
|Shear modulus||47 GPa|
|Bulk modulus||160 GPa|
|Vickers hardness||628–640 MPa|
|Brinell hardness||600–742 MPa|
|Discovery||Nils Gabriel Sefström (1830)|
|First isolation||Henry Enfield Roscoe (1867)|
|Named by||Nils Gabriel Sefström (1830)|
|Main isotopes of vanadium|
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer (passivation) somewhat stabilizes the free metal 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". Though he initially presumed its qualities were due to the presence of a new element, he was later erroneously convinced by French chemist Hippolyte Victor Collet-Descotils that the element was just chromium. Then in 1830, Nils Gabriel Sefström generated chlorides of vanadium, thus proving there was a new element, and named it "vanadium" after the Scandinavian goddess of beauty and fertility, Vanadís (Freyja). The name was based on the wide range of colors found in vanadium compounds. Del Rio's lead mineral was ultimately named vanadinite for its vanadium content. In 1867 Henry Enfield Roscoe obtained the pure element.
Vanadium occurs naturally in about 65 minerals and in fossil fuel deposits. It is produced in China and Russia from steel smelter slag. Other countries produce it either from magnetite directly, 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, and some aluminium alloys. The most important industrial vanadium compound, vanadium pentoxide, is used as a catalyst for the production of sulfuric acid. The vanadium redox battery for energy storage may be an important application in the future.
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.
Vanadium was discovered in 1801 by the Spanish mineralogist Andrés Manuel del Río. Del Río extracted the element from a sample of Mexican "brown lead" ore, later named vanadinite. He found that its salts exhibit a wide variety of colors, and as a result he named the element panchromium (Greek: παγχρώμιο "all colors"). Later, Del Río renamed the element erythronium (Greek: ερυθρός "red") because most of the salts turned red upon heating. In 1805, French chemist Hippolyte Victor Collet-Descotils, backed by del Río's friend Baron Alexander von Humboldt, incorrectly declared that del Río's new element was an impure sample of chromium. Del Río accepted Collet-Descotils' statement and retracted his claim.
In 1831 Swedish chemist Nils Gabriel Sefström rediscovered the element in a new oxide he found while working with iron ores. Later that year, Friedrich Wöhler confirmed del Río's earlier work.Sefström chose a name beginning with V, which had not yet been assigned to any element. He called the element vanadium after Old Norse Vanadís (another name for the Norse Vanr goddess Freyja, whose attributes include beauty and fertility), because of the many beautifully colored chemical compounds it produces. In 1831, the geologist George William Featherstonhaugh suggested that vanadium should be renamed "rionium" after del Río, but this suggestion was not followed.
The isolation of vanadium metal was difficult.[ citation needed ] In 1831, Berzelius reported the production of the metal, but Henry Enfield Roscoe showed that Berzelius had produced the nitride, vanadium nitride (VN). Roscoe eventually produced the metal in 1867 by reduction of vanadium(II) chloride, VCl2, with hydrogen. In 1927, pure vanadium was produced by reducing vanadium pentoxide with calcium.
The first large-scale industrial use of vanadium was in the steel alloy chassis of the Ford Model T, inspired by French race cars. Vanadium steel allowed reduced weight while increasing tensile strength (ca. 1905).For the first decade of the 20th century, most vanadium ore was mined by American Vanadium Company from the Minas Ragra in Peru. Later, the demand for uranium rose, leading to increased mining of that metal's ores. One major uranium ore was carnotite, which also contains vanadium. Thus, vanadium became available as a by-product of uranium production. Eventually, uranium mining began to supply a large share of the demand for vanadium.
In 1911, German chemist Martin Henze discovered vanadium in the hemovanadin proteins found in blood cells (or coelomic cells) of Ascidiacea (sea squirts).
Vanadium is a medium-hard, ductile, steel-blue metal. It is electrically conductive and thermally insulating. Some sources describe vanadium as "soft", perhaps because it is ductile, malleable, and not brittle. K (660 °C, 1220 °F), although an oxide passivation layer forms even at room temperature.Vanadium is harder than most metals and steels (see Hardnesses of the elements (data page) and iron). It has good resistance to corrosion and it is stable against alkalis and sulfuric and hydrochloric acids. It is oxidized in air at about 933
Naturally occurring vanadium is composed of one stable isotope, 51V, and one radioactive isotope, 50V. The latter has a half-life of 1.5×1017 years and a natural abundance of 0.25%. 51V has a nuclear spin of 7⁄2, which is useful for NMR spectroscopy. Twenty-four artificial radioisotopes have been characterized, ranging in mass number from 40 to 65. The most stable of these isotopes are 49V with a half-life of 330 days, and 48V with a half-life of 16.0 days. The remaining radioactive isotopes have half-lives shorter than an hour, most below 10 seconds. At least four isotopes have metastable excited states. Electron capture is the main decay mode for isotopes lighter than 51V. For the heavier ones, the most common mode is beta decay. The electron capture reactions lead to the formation of element 22 (titanium) isotopes, while beta decay leads to element 24 (chromium) isotopes.
The chemistry of vanadium is noteworthy for the accessibility of the four adjacent oxidation states 2–5. In aqueous solution, vanadium forms metal aquo complexes of which the colours are lilac [V(H2O)6]2+, green [V(H2O)6]3+, blue [VO(H2O)5]2+, yellow-orange oxides, the formula for which depends on pH . Vanadium(II) compounds are reducing agents, and vanadium(V) compounds are oxidizing agents. Vanadium(IV) compounds often exist as vanadyl derivatives, which contain the VO2+ center.
Ammonium vanadate(V) (NH4VO3) can be successively reduced with elemental zinc to obtain the different colors of vanadium in these four oxidation states. Lower oxidation states occur in compounds such as V(CO)6, [V(CO)
and substituted derivatives.
Vanadium pentoxide is a commercially important catalyst for the production of sulfuric acid, a reaction that exploits the ability of vanadium oxides to undergo redox reactions.
The vanadium redox battery utilizes all four oxidation states: one electrode uses the +5/+4 couple and the other uses the +3/+2 couple. Conversion of these oxidation states is illustrated by the reduction of a strongly acidic solution of a vanadium(V) compound with zinc dust or amalgam. The initial yellow color characteristic of the pervanadyl ion [VO2(H2O)4]+ is replaced by the blue color of [VO(H2O)5]2+, followed by the green color of [V(H2O)6]3+ and then the violet color of [V(H2O)6]2+.
In aqueous solution, vanadium(V) forms an extensive family of oxyanions as established by 51V NMR spectroscopy. VO3−
4, is the principal species present at pH 12–14. Similar in size and charge to phosphorus(V), vanadium(V) also parallels its chemistry and crystallography. Orthovanadate VO3−
4 is used in protein crystallography to study the biochemistry of phosphate. The tetrathiovanadate [VS4]3− is analogous to the orthovanadate ion.
At lower pH values, the monomer [HVO4]2− and dimer [V2O7]4− are formed, with the monomer predominant at vanadium concentration of less than c. 10−2M (pV > 2, where pV is equal to the minus value of the logarithm of the total vanadium concentration/M). The formation of the divanadate ion is analogous to the formation of the dichromate ion. As the pH is reduced, further protonation and condensation to polyvanadates occur: at pH 4-6 [H2VO4]− is predominant at pV greater than ca. 4, while at higher concentrations trimers and tetramers are formed. Between pH 2-4 decavanadate predominates, its formation from orthovanadate is represented by this condensation reaction:
In decavanadate, each V(V) center is surrounded by six oxide ligands. < 2, [VO2(H2O)4]+ is the predominant species, while the oxide V2O5 precipitates from solution at high concentrations. The oxide is formally the acid anhydride of vanadic acid. The structures of many vanadate compounds have been determined by X-ray crystallography.Vanadic acid, H3VO4 exists only at very low concentrations because protonation of the tetrahedral species [H2VO4]− results in the preferential formation of the octahedral [VO2(H2O)4]+ species. In strongly acidic solutions, pH
Vanadium(V) forms various peroxo complexes, most notably in the active site of the vanadium-containing bromoperoxidase enzymes. The species VO(O)2(H2O)4+ is stable in acidic solutions. In alkaline solutions, species with 2, 3 and 4 peroxide groups are known; the last forms violet salts with the formula M3V(O2)4 nH2O (M= Li, Na, etc.), in which the vanadium has an 8-coordinate dodecahedral structure.
Twelve binary halides, compounds with the formula VXn (n=2..5), are known. VI4, VCl5, VBr5, and VI5 do not exist or are extremely unstable. In combination with other reagents, VCl4 is used as a catalyst for polymerization of dienes. Like all binary halides, those of vanadium are Lewis acidic, especially those of V(IV) and V(V). Many of the halides form octahedral complexes with the formula VXnL6−n (X= halide; L= other ligand).
Many vanadium oxyhalides (formula VOmXn) are known.The oxytrichloride and oxytrifluoride (VOCl3 and VOF3) are the most widely studied. Akin to POCl3, they are volatile, adopt tetrahedral structures in the gas phase, and are Lewis acidic.
Complexes of vanadium(II) and (III) are relatively exchange inert and reducing. Those of V(IV) and V(V) are oxidants. Vanadium ion is rather large and some complexes achieve coordination numbers greater than 6, as is the case in [V(CN)7]4−. Oxovanadium(V) also forms 7 coordinate coordination complexes with tetradentate ligands and peroxides and these complexes are used for oxidative brominations and thioether oxidations. The coordination chemistry of V4+ is dominated by the vanadyl center, VO2+, which binds four other ligands strongly and one weakly (the one trans to the vanadyl center). An example is vanadyl acetylacetonate (V(O)(O2C5H7)2). In this complex, the vanadium is 5-coordinate, square pyramidal, meaning that a sixth ligand, such as pyridine, may be attached, though the association constant of this process is small. Many 5-coordinate vanadyl complexes have a trigonal bipyramidal geometry, such as VOCl2(NMe3)2.The coordination chemistry of V5+ is dominated by the relatively stable dioxovanadium coordination complexes which are often formed by aerial oxidation of the vanadium(IV) precursors indicating the stability of the +5 oxidation state and ease of interconversion between the +4 and +5 states.
Organometallic chemistry of vanadium is well developed, although it has mainly only academic significance.[ citation needed ] Vanadocene dichloride is a versatile starting reagent and has applications in organic chemistry. Vanadium carbonyl, V(CO)6, is a rare example of a paramagnetic metal carbonyl. Reduction yields V(CO)−
6 (isoelectronic with Cr(CO)6), which may be further reduced with sodium in liquid ammonia to yield V(CO)3−
5 (isoelectronic with Fe(CO)5).
The cosmic abundance of vanadium in the universe is 0.0001%, making the element nearly as common as copper or zinc.Vanadium is detected spectroscopically in light from the Sun and sometimes in the light from other stars.
Vanadium is the 20th most abundant element in the earth's crust;metallic vanadium is rare in nature (known as native vanadium), but vanadium compounds occur naturally in about 65 different minerals.
At the beginning of the 20th century a large deposit of vanadium ore was discovered, the Minas Ragra vanadium mine near Junín, Cerro de Pasco, Peru. K2(UO2)2(VO4)2·3H2O) vanadium became available as a side product of uranium production. Vanadinite (Pb5(VO4)3Cl) and other vanadium bearing minerals are only mined in exceptional cases. With the rising demand, much of the world's vanadium production is now sourced from vanadium-bearing magnetite found in ultramafic gabbro bodies. If this titanomagnetite is used to produce iron, most of the vanadium goes to the slag, and is extracted from it.For several years this patrónite (VS4) deposit was an economically significant source for vanadium ore. In 1920 roughly two thirds of the worldwide production was supplied by the mine in Peru. With the production of uranium in the 1910s and 1920s from carnotite (
Vanadium is mined mostly in South Africa, north-western China, and eastern Russia. In 2013 these three countries mined more than 97% of the 79,000 tonnes of produced vanadium.
Vanadium is also present in bauxite and in deposits of crude oil, coal, oil shale, and tar sands. In crude oil, concentrations up to 1200 ppm have been reported. When such oil products are burned, traces of vanadium may cause corrosion in engines and boilers. An estimated 110,000 tonnes of vanadium per year are released into the atmosphere by burning fossil fuels. Black shales are also a potential source of vanadium. During WW II some vanadium was extracted from alum shales in the south of Sweden.
The vanadyl ion is abundant in seawater, having an average concentration of 30 nM (1.5 mg/m3). Some mineral water springs also contain the ion in high concentrations. For example, springs near Mount Fuji contain as much as 54 μg per liter.
Vanadium metal is obtained by a multistep process that begins with roasting crushed ore with NaCl or Na2CO3 at about 850 °C to give sodium metavanadate (NaVO3). An aqueous extract of this solid is acidified to produce "red cake", a polyvanadate salt, which is reduced with calcium metal. As an alternative for small-scale production, vanadium pentoxide is reduced with hydrogen or magnesium. Many other methods are also used, in all of which vanadium is produced as a byproduct of other processes. Purification of vanadium is possible by the crystal bar process developed by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925. It involves the formation of the metal iodide, in this example vanadium(III) iodide, and the subsequent decomposition to yield pure metal:
Most vanadium is used as a steel alloy called ferrovanadium. Ferrovanadium is produced directly by reducing a mixture of vanadium oxide, iron oxides and iron in an electric furnace. The vanadium ends up in pig iron produced from vanadium-bearing magnetite. Depending on the ore used, the slag contains up to 25% of vanadium.
Approximately 85% of the vanadium produced is used as ferrovanadium or as a steel additive.The considerable increase of strength in steel containing small amounts of vanadium was discovered in the early 20th century. Vanadium forms stable nitrides and carbides, resulting in a significant increase in the strength of steel. From that time on, vanadium steel was used for applications in axles, bicycle frames, crankshafts, gears, and other critical components. There are two groups of vanadium steel alloys. Vanadium high-carbon steel alloys contain 0.15% to 0.25% vanadium, and high-speed tool steels (HSS) have a vanadium content of 1% to 5%. For high-speed tool steels, a hardness above HRC 60 can be achieved. HSS steel is used in surgical instruments and tools. Powder-metallurgic alloys contain up to 18% percent vanadium. The high content of vanadium carbides in those alloys increases wear resistance significantly. One application for those alloys is tools and knives.
Vanadium stabilizes the beta form of titanium and increases the strength and temperature stability of titanium. Mixed with aluminium in titanium alloys, it is used in jet engines, high-speed airframes and dental implants. The most common alloy for seamless tubing is Titanium 3/2.5 containing 2.5% vanadium, the titanium alloy of choice in the aerospace, defense, and bicycle industries.Another common alloy, primarily produced in sheets, is Titanium 6AL-4V, a titanium alloy with 6% aluminium and 4% vanadium.
Several vanadium alloys show superconducting behavior. The first A15 phase superconductor was a vanadium compound, V3Si, which was discovered in 1952.Vanadium-gallium tape is used in superconducting magnets (17.5 teslas or 175,000 gauss). The structure of the superconducting A15 phase of V3Ga is similar to that of the more common Nb3Sn and Nb3Ti.
It has been found that a small amount, 40 to 270 ppm, of vanadium in Wootz steel significantly improved the strength of the product, and gave it the distinctive patterning. The source of the vanadium in the original Wootz steel ingots remains unknown.
Vanadium compounds are used extensively as catalysts; SO
2) is oxidized to the trioxide (SO
3): In this redox reaction, sulfur is oxidized from +4 to +6, and vanadium is reduced from +5 to +4:
The catalyst is regenerated by oxidation with air:
Similar oxidations are used in the production of maleic anhydride:
Phthalic anhydride and several other bulk organic compounds are produced similarly. These green chemistry processes convert inexpensive feedstocks to highly functionalized, versatile intermediates.
Vanadium is an important component of mixed metal oxide catalysts used in the oxidation of propane and propylene to acrolein, acrylic acid or the ammoxidation of propylene to acrylonitrile.In service, the oxidation state of vanadium changes dynamically and reversibly with the oxygen and the steam content of the reacting feed mixture.
Another oxide of vanadium, vanadium dioxide VO2, is used in the production of glass coatings, which blocks infrared radiation (and not visible light) at a specific temperature.Vanadium oxide can be used to induce color centers in corundum to create simulated alexandrite jewelry, although alexandrite in nature is a chrysoberyl. Vanadium pentoxide is used in ceramics.
The vanadium redox battery, a type of flow battery, is an electrochemical cell consisting of aqueous vanadium ions in different oxidation states.Batteries of the type were first proposed in the 1930s and developed commercially from the 1980s onwards. Cells use +5 and +2 formal oxidization state ions. Vanadium redox batteries are used commercially for grid energy storage.
Vanadate can be used for protecting steel against rust and corrosion by conversion coating.Vanadium foil is used in cladding titanium to steel because it is compatible with both iron and titanium. The moderate thermal neutron-capture cross-section and the short half-life of the isotopes produced by neutron capture makes vanadium a suitable material for the inner structure of a fusion reactor.
Lithium vanadium oxide has been proposed for use as a high energy density anode for lithium ion batteries, at 745 Wh/L when paired with a lithium cobalt oxide cathode. Vanadium phosphates have been proposed as the cathode in the lithium vanadium phosphate battery, another type of lithium-ion battery.
Vanadium is more important in marine environments than terrestrial.
A number of species of marine algae produce vanadium bromoperoxidase as well as the closely related chloroperoxidase (which may use a heme or vanadium cofactor) and iodoperoxidases. The bromoperoxidase produces an estimated 1–2 million tons of bromoform and 56,000 tons of bromomethane annually.Most naturally occurring organobromine compounds are produced by this enzyme, catalyzing the following reaction (R-H is hydrocarbon substrate):
A vanadium nitrogenase is used by some nitrogen-fixing micro-organisms, such as Azotobacter . In this role, vanadium replaces more-common molybdenum or iron, and gives the nitrogenase slightly different properties.
Vanadium is essential to tunicates, where it is stored in the highly acidified vacuoles of certain blood cell types, designated vanadocytes. Vanabins (vanadium binding proteins) have been identified in the cytoplasm of such cells. The concentration of vanadium in the blood of ascidian tunicates is as much as ten million times higher[ specify ] than the surrounding seawater, which normally contains 1 to 2 µg/l. The function of this vanadium concentration system and these vanadium-bearing proteins is still unknown, but the vanadocytes are later deposited just under the outer surface of the tunic, where they may deter predation.
Amanita muscaria and related species of macrofungi accumulate vanadium (up to 500 mg/kg in dry weight). Vanadium is present in the coordination complex amavadin in fungal fruit-bodies. The biological importance of the accumulation is unknown. Toxic or peroxidase enzyme functions have been suggested.
Deficiencies in vanadium result in reduced growth in rats. µg/day, with less than 5% absorbed. The Tolerable Upper Intake Level (UL) of dietary vanadium, beyond which adverse effects may occur, is set at 1.8 mg/day.The U.S. Institute of Medicine has not confirmed that vanadium is an essential nutrient for humans, so neither a Recommended Dietary Intake nor an Adequate Intake have been established. Dietary intake is estimated at 6 to 18
Vanadyl sulfate as a dietary supplement has been researched as a means of increasing insulin sensitivity or otherwise improving glycemic control in people who are diabetic. Some of the trials had significant treatment effects, but were deemed as being of poor study quality. The amounts of vanadium used in these trials (30 to 150 mg) far exceeded the safe upper limit. The conclusion of the systemic review was "There is no rigorous evidence that oral vanadium supplementation improves glycaemic control in type 2 diabetes. The routine use of vanadium for this purpose cannot be recommended."
In astrobiology, it has been suggested that discrete vanadium accumulations on Mars could be a potential microbial biosignature, when used in conjunction with Raman spectroscopy and morphology.
All vanadium compounds should be considered toxic. Tetravalent VOSO4 has been reported to be at least 5 times more toxic than trivalent V2O3. 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, that is, likely to cause permanent health problems or death.The Occupational Safety and Health Administration (OSHA) has set an exposure limit of 0.05
Vanadium compounds are poorly absorbed through the gastrointestinal system. Inhalation of vanadium and vanadium compounds results primarily in adverse effects on the respiratory system.Quantitative data are, however, insufficient to derive a subchronic or chronic inhalation reference dose. Other effects have been reported after oral or inhalation exposures on blood parameters, liver, neurological development, and other organs in rats.
There is little evidence that vanadium or vanadium compounds are reproductive toxins or teratogens. Vanadium pentoxide was reported to be carcinogenic in male rats and in male and female mice by inhalation in an NTP study,although the interpretation of the results has recently been disputed. The carcinogenicity of vanadium has not been determined by the United States Environmental Protection Agency.
Vanadium traces in diesel fuels are the main fuel component in high temperature corrosion. During combustion, vanadium oxidizes and reacts with sodium and sulfur, yielding vanadate compounds with melting points as low as 530 °C, which attack the passivation layer on steel and render it susceptible to corrosion. The solid vanadium compounds also abrade engine components.
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element.
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium is the main additive in stainless steel, to which it adds anti-corrosive properties. Chromium is also highly valued as a metal that is able to be highly polished while resisting tarnishing. Polished chromium reflects almost 70% of the visible spectrum, with almost 90% of infrared light being reflected. The name of the element is derived from the Greek word χρῶμα, chrōma, meaning color, because many chromium compounds are intensely colored.
Erbium is a chemical element with the symbol Er and atomic number 68. A silvery-white solid metal when artificially isolated, natural erbium is always found in chemical combination with other elements. It is a lanthanide, a rare earth element, originally found in the gadolinite mine in Ytterby in Sweden, from which it got its name.
Carbon compounds are defined as chemical substances containing carbon. More compounds of carbon exist than any other chemical element except for hydrogen. Organic carbon compounds are far more numerous than inorganic carbon compounds. In general bonds of carbon with other elements are covalent bonds. Carbon is tetravalent but carbon free radicals and carbenes occur as short-lived intermediates. Ions of carbon are carbocations and carbanions are also short-lived. An important carbon property is catenation as the ability to form long carbon chains and rings.
Niobium, also known as columbium, is a chemical element with the symbol Nb and atomic number 41. Niobium is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to that of pure titanium, and it has similar ductility to iron. Niobium oxidizes in the earth's atmosphere very slowly, hence its application in jewelry as a hypoallergenic alternative to nickel. Niobium is often found in the minerals pyrochlore and columbite, hence the former name "columbium". Its name comes from Greek mythology, specifically Niobe, who was the daughter of Tantalus, the namesake of tantalum. The name reflects the great similarity between the two elements in their physical and chemical properties, making them difficult to distinguish.
An oxide is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. Metal oxides thus typically contain an anion of oxygen in the oxidation state of −2. Most of the Earth's crust consists of solid oxides, the result of elements being oxidized by the oxygen in air or in water. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 (called a passivation layer) that protects the foil from further corrosion. Certain elements can form multiple oxides, differing in the amounts of the element combining with the oxygen. Examples are carbon, iron, nitrogen (see nitrogen oxide), silicon, titanium, and aluminium. In such cases the oxides are distinguished by specifying the numbers of atoms involved, as in carbon monoxide and carbon dioxide, or by specifying the element's oxidation number, as in iron(II) oxide and iron(III) oxide.
Titanium is a chemical element with the symbol Ti and atomic number 22. Its atomic weight is 47.867 measured in daltons. It is a lustrous transition metal with a silver color, low density, and high strength. Titanium is resistant to corrosion in sea water, aqua regia, and chlorine.
Group 5 is a group of elements in the periodic table. Group 5 contains vanadium (V), niobium (Nb), tantalum (Ta) and dubnium (Db). This group lies in the d-block of the periodic table. The group itself has not acquired a trivial name; it belongs to the broader grouping of the transition metals.
Vanadium(V) oxide (vanadia) is the inorganic compound with the formula V2O5. Commonly known as vanadium pentoxide, it is a brown/yellow solid, although when freshly precipitated from aqueous solution, its colour is deep orange. Because of its high oxidation state, it is both an amphoteric oxide and an oxidizing agent. From the industrial perspective, it is the most important compound of vanadium, being the principal precursor to alloys of vanadium and is a widely used industrial catalyst.
In chemistry, a vanadate is an anionic coordination complex of vanadium. Often vanadate refers to oxoanions of vanadium, most of which exist in its highest oxidation state of +5. The complexes [V(CN)6]3- and [V2Cl9]3- are referred to as hexacyanovanadate and nonachlorodivanadate.
Vanadium oxytrichloride is the inorganic compound with the formula VOCl3. This yellow distillable liquid hydrolyzes readily in air. It is an oxidizing agent. It is used as a reagent in organic synthesis. Samples often appear red or orange owing to an impurity of vanadium tetrachloride.
In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually restricted to small ligands such as pseudohalides or to ligands that are specifically designed to link two metals.
Vanadium(IV) oxide or vanadium dioxide is an inorganic compound with the formula VO2. It is a dark blue solid. Vanadium(IV) dioxide is amphoteric, dissolving in non-oxidising acids to give the blue vanadyl ion, [VO]2+ and in alkali to give the brown [V4O9]2− ion, or at high pH [VO4]4−. VO2 has a phase transition very close to room temperature (~66 °C). Electrical resistivity, opacity, etc, can change up several orders. Owing to these properties, it has been used in surface coating, sensors, and imaging. Potential applications include use in memory devices, phase-change switches, aerospace communication systems and neuromorphic computing.
Vanadyl(IV) sulfate describes a collection of inorganic compounds of vanadium with the formula, VOSO4(H2O)x where 0 ≤ x ≤ 6. The pentahydrate is common. This hygroscopic blue solid is one of the most common sources of vanadium in the laboratory, reflecting its high stability. It features the vanadyl ion, VO2+, which has been called the "most stable diatomic ion".
The vanadyl or oxovanadium(IV) cation, VO2+, is a functional group that is common in the coordination chemistry of vanadium. Complexes containing this functional group are characteristically blue and paramagnetic. A triple bond is proposed to exist between the V4+ and O2- centers. The description of the bonding in the vanadyl ion was central to the development of modern ligand-field theory.
Vanadyl acetylacetonate is the chemical compound with the formula VO(acac)2, where acac– is the conjugate base of acetylacetone. It is a blue-green solid that dissolves in polar organic solvents. The coordination complex consists of the vanadyl group, VO2+, bound to two acac– ligands via the two oxygen atoms on each. Like other charge-neutral acetylacetonate complexes, it is not soluble in water.
Metal aquo complexes are coordination compounds containing metal ions with only water as a ligand. These complexes are the predominant species in aqueous solutions of many metal salts, such as metal nitrates, sulfates, and perchlorates. They have the general stoichiometry [M(H
n]z+. Their behavior underpins many aspects of environmental, biological, and industrial chemistry. This article focuses on complexes where water is the only ligand, but of course many complexes are known to consist of a mix of aquo and other ligands.
Vanadyl nitrate, also called vanadium oxytrinitrate or vanadium oxynitrate is a compound of vanadium in the +5 oxidation state with nitrate groups and oxygen. The formula is VO(NO3)3. It is made from dinitrogen pentoxide and vanadium pentoxide. It is a nitrating agent, adding nitro groups to aromatic compounds such as benzene, phenol, chlorobenzene, anisole, acetanilide, benzoic acid, ethyl benzoate, and toluene.
Vanadyl perchlorate or vanadyl triperchlorate is a golden yellow coloured liquid or crystalline compound of vanadium, oxygen and perchlorate group. The substance consists of molecules covalently bound and is quite volatile.
Vanadium phosphates are inorganic compounds with the formula VOxPO4 as well related hydrates with the formula VOxPO4(H2O)n. Some of these compounds are used commercially as catalysts for oxidation reactions.
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