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Vanadium (pronounced /vəˈneɪdiəm/) is the chemical element with the symbol V and atomic number 23. It is a soft, silvery grey, ductile transition metal. The formation of an oxide layer stabilizes the metal against oxidation. Andrés Manuel del Río discovered vanadium in 1801 by analyzing the mineral vanadinite, and named it erythronium. Four years later, however, he was convinced by other scientists that erythronium was identical to chromium. The element was rediscovered in 1831 by Nils Gabriel Sefström, who named it vanadium after the Norse goddess of beauty and fertility, Vanadis (Freya). Both names were attributed to the wide range of colors found in vanadium compounds.

The element 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 compound vanadium pentoxide is used as a catalyst for the production of sulfuric acid. Vanadium is found in many organisms, and is used by some life forms as an active center of enzymes.

History

Vanadium was originally discovered by Andrés Manuel del Río, a Spanish-born Mexican mineralogist, in 1801. 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: all colors). Later, Del Río renamed the element erythronium as most of its salts turned red upon heating. In 1805, the 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 only an impure sample of chromium. Del Río accepted the Collet-Descotils' statement, and retracted his claim.[1]

In 1831, the Swedish chemist, Nils Gabriel Sefström, rediscovered the element in a new oxide he found while working with iron ores. Later that same year, Friedrich Wöhler confirmed del Río's earlier work.[2] Sefström choose a name beginning with V, which had not been assigned to any element yet. He called the element vanadium after Vanadis (another name for Freya, the Norse goddess of beauty and fertility), because of the many beautifully colored chemical compounds it produces.[2] In 1831, the geologist George William Featherstonhaugh suggested that vanadium should be renamed "rionium" after del Río, but this suggestion was not followed.[3]

The isolation of vanadium metal proved difficult. In 1831, Berzelius reported the production of the metal, but Henry Enfield Roscoe showed that Berzelius had in fact produced the nitride, vanadium nitride (VN). Roscoe eventually produced the metal in 1867 by reduction of vanadium(III) chloride, VCl3, with hydrogen.[4] In 1927, pure vanadium was produced by reducing vanadium pentoxide with calcium.[5] The first large scale industrial use of vanadium in steels was found in the chassis of the Ford Model T, inspired by French race cars. Vanadium steel allowed for reduced weight while simultaneously increasing tensile strength.[6]

Characteristics
Vanadium is a soft, ductile, silver-grey metal. It has good resistance to corrosion and it is stable against alkalis, sulfuric and hydrochloric acids.[7] It is oxidized in air at about 933 K (660 °C, 1220 °F), although an oxide layer forms even at room temperature.
Isotopes
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 0.25%. 51V has a nuclear spin of 7/2 which is useful for NMR spectroscopy.[8] A number of 24 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 15.9735 days. All of the remaining radioactive isotopes have half-lives shorter than an hour, most of which are below 10 seconds. At least 4 isotopes have metastable excited states.[8] Electron capture is the main decay mode for isotopes lighter than the 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 for beta decay, it leads to element 24 (chromium) isotopes.

Chemistry and compounds
The chemistry of vanadium is noteworthy for the accessibility of four adjacent oxidation states. The common oxidation states of vanadium are +2 (lilac), +3 (green), +4 (blue) and +5 (yellow). 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.[7]

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)6]- and substituted derivatives.[7]

The vanadium redox battery utilizes these oxidation states; conversions of these oxidation states is illustrated by the reduction of a strongly acidic solution of a vanadium(V) compound with zinc dust. The initial yellow color characteristic of the vanadate ion, VO43−, is replaced by the blue color of [VO(H2O)5]2+, followed by the green color of [V(H2O)6]3+ and then violet, due to [V(H2O)6]2+.[7]

The most commercially important compound is vanadium pentoxide, which is used as a catalyst for the production of sulfuric acid.[7] This compound oxidizes sulfur dioxide (SO2) to the trioxide (SO3). In this redox reaction, sulfur is oxidized from +4 to +6, and vanadium is reduced from +5 to +3:

Oxy and oxo compounds
The oxyanion chemistry of vanadium(V) is complex. The vanadate ion, VO43?, is present in dilute solutions at high pH. On acidification, HVO42- and H2VO4- are formed, analogous to HPO42- and H2PO4-. The acid dissociation constants for the vanadium and phosphorus series are remarkably similar. In more concentrated solutions many polyvanadates are formed. Chains, rings and clusters involving tetrahedral vanadium, analogous to the polyphosphates, are known. In addition, clusters such as the decavanadates V10O284? and HV10O283?, which predominate at pH 4-6, are formed in which compound is octahedral about vanadium.[7]

The correspondence between vanadate and phosphate chemistry can be attributed to the similarity in size and charge of phosphorus(V) and vanadium(V). Orthovanadate VO43? is used in protein crystallography[10] to study the biochemistry of phosphate.[11]

Halide compounds
Several halides are known for oxidation states +2, +3 and +4. VCl4 is the most important commercially. This liquid is mainly used as a catalyst for polymerization of dienes.

Coordination compounds
Vanadium's early position in the transition metal series lead to three rather unusual features of the coordination chemistry of vanadium. Firstly, metallic vanadium has the electronic configuration [Ar]4s23d3, so compounds of vanadium are relatively electron-poor. Consequently, most binary compounds are Lewis acids (electron pair acceptors); examples are all the halides forming octahedral adducts with the formula VXnL6-n (X = halide; L = other ligand). Secondly, the vanadium ion is rather large and can achieve coordination numbers higher than 6, as is the case in [V(CN)7]4−. Thirdly, the vanadyl ion, VO2+, is featured in many complexes of vanadium(IV) such as vanadyl acetylacetonate (V(=O)(acac)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 bypyramidal geometry, such as VO(Cl2(NMe3)2.[12]

Organometallic compounds
Organometallic chemistry of vanadium is well developed, but organometallic compounds are of minor commercial significance. Vanadocene dichloride is a versatile starting reagent and even finds minor applications in organic chemistry.[13] Vanadium carbonyl, V(CO)6, is a rare example of a metal carbonyl containing an unpaired electron, but which exists without dimerization. The addition of an electron yields V(CO)6− (isoelectronic with Cr(CO)6), which may be further reduced with sodium in liquid ammonia to yield V(CO)53− (isoelectronic with Fe(CO)5).[14][15]

Occurrence
Metallic vanadium is not found in nature, but is known to exist in about 65 different minerals. Economically significant examples include patronite (VS4),[16] vanadinite (Pb5(VO4)3Cl), and carnotite (K2(UO2)2(VO4)2·3H2O). Much of the world's vanadium production is sourced from vanadium-bearing magnetite found in ultramafic gabbro bodies. Vanadium is mined mostly in South Africa, north-western China, and eastern Russia. In 2007 these three countries mined more than 95 % of the 58,600 tonnes of produced vanadium.[17]

Vanadium is also present in bauxite and in fossil fuel deposits such as 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, the traces of vanadium may initiate corrosion in motors and boilers.[18] An estimated 110,000 tonnes of vanadium per year are released into the atmosphere by burning fossil fuels.[19] Vanadium has also been detected spectroscopically in light from the Sun and some other stars.[20]

Production
Most vanadium is used as ferrovanadium as an additive to improve steels. Ferrovanadium is produced directly by reducing a mixture of vanadium oxide, iron oxides and iron in an electric furnace. Vanadium-bearing magnetite iron ore is the main source for the production of vanadium.[21] The vanadium ends up in pig iron produced from vanadium bearing magnetite. During steel production, oxygen is blown into the pig iron, oxidizing the carbon and most of the other impurities, forming slag. Depending on the used ore, the slag contains up to 25% of vanadium.[21]

Vanadium metal is obtained via a multistep process that begins with the roasting of crushed ore with NaCl or Na2CO3 at about 850 °C to give sodium metavanadate (NaVO3). An aqueous extract of this solid is acidified to give "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 in use, in all of which vanadium is produced as a byproduct of other processes.[21] 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.[22]

钒

钒是一种化学元素，它的化学符号是V，它的原子序数是23。钒是中文从英语的Vanadium音译过来的，其词根来源于古日耳曼语中日耳曼神话中美丽女神的名字Vanadis。这个名字来源于钒的许多色彩鲜艳的化合物。

钒是一种稀有的，柔弱而黏稠的过渡金属。它的矿物一般与其它金属的矿物混合在一起。它一般被用在材料工程中作为合金的成分。

同位素
主条目：钒的同位素

特性
钒是一种非磁性的、黏稠的、可涂抹的银灰色的过度性金属。它不易腐蚀，在碱、硫酸和盐酸中它相当稳定。在933K（660°C）以上的温度中它氧化为五氧化二钒V2O5。钒的结构强度相当高。

在氧化物中钒一般显+5价，但也有+2、+3和+4价的氧化物存在，不过它们比较容易过渡为+5价的氧化物。2价和3价的钒氧化物是碱性的，4价的氧化物是双性的，5价的氧化物是酸性的。

一个很有趣的试验是用锌来还原无色的钒酸氨（NH4VO3）。在试验的过程中钒相继被还原成蓝色的四价钒、绿色的三价钒、紫蓝色的二价钒，随后低价的钒又会被空气中的氧氧化为无色的五价钒（五价钒应该是橙色的）。由于钒的价数很容易改变，它也经常被用做催化剂。+1价的钒很少出现。理论上0、-1和-3价的钒也有可能。

应用
大约80%的钒和铁一起作为钢里的合金元素。含钒的钢很硬很坚实，但一般其钒含量少于1%。

含钒的合金有：
运用在医疗器械中的特别的不锈钢
运用在工具中的不锈钢
与铝一起作为钛合金物运用在高速飞机的涡轮喷气发动机中
含钒的钢经常被用在轴、齿轮等关键的机械部分中
钒吸收裂变中子的半径很小，因此被用在核工业中
在炼钢过程中钒被用来导致碳化物的形成
在给钢涂钛的时候钒往往被作为中介层
钒与镓的合金可以用来制作超导电磁铁，其磁强度可达175,000高斯
在制造缩苹果酸酐和硫酸的过程中钒被用来做催化剂
五氧化二钒（V2O5）被用来制做特殊的陶瓷作为催化剂

历史
1801年一个叫安德列斯·曼努尔·德·里欧（A.M.Del-Rio）的矿物学家在墨西哥市在一个铅矿中首先发现了钒，但他错误地以为他所发现的只不过是一种不纯的铬。1831年瑞典人尼尔斯·加布里埃尔·塞夫斯特瑞姆（N.G.Sefström）在与铁矿做试验时重新发现了钒，同年弗里德里希·维勒证实了德·里欧的发现。1867年亨利·英弗尔德·罗斯科用氢还原亚氯酸化钒（III）首次得到了纯的钒。

塞夫斯特瑞姆给钒按日尔曼神话中美丽女神的名字起了名，因为钒的化合物色彩缤纷。

生理
在生物体内钒是一些酶的必要组成部分。一些固氮的微生物使用含钒的酶来固定空气中的氮。

鼠和鸡也需要少量的钒，缺钒会阻碍它们的生长和繁殖。含钒的血红蛋白存在于海鞘类动物中。

一些含钒的物质具有类似胰岛素的效应，也许可以用来治疗糖尿病。

来源
在大自然中钒一般以化合物存在。约65种钒的化合物在自然中出现，其中有

硫化钒（VS4）
绿硫钒矿（VS2或V2S4）
钒铅矿（Pb5(VO4)3Cl）
钒云母KV2（AlSi3O10）（OH）2
钒酸钾铀矿（K2(UO2)2(VO4)2·3H2O）
磁铁矿一般含1-2%的钒
在矾土和石油、煤、油页岩中也含有大量钒，特别是委内瑞拉和加拿大的石油中能找到钒。光谱分析发现在太阳光和一些恒星的表面也有钒。
生产
纯的金属钒一般是用钾在高压下将五氧化二钒还原而得到的。大多数钒是其它矿物加工时的副产品。

化合物
五氧化二钒是钒最重要的化合物，常被用来做催化剂、染料和固色剂。它加热可放出氧气，而这个反应是可逆的。有了这个性质，令它可催化二氧化硫、苯和萘的氧化反应，在工业上应用来制造硫酸、邻苯二甲酐和顺丁烯二酐。橙色的它是有毒的。它是两性的，也是氧化剂。许多金属的氧化物都不溶于水，它却微溶于水