The vanadium It is the third transition metal in the periodic table, represented by the chemical symbol V. It is not as popular as other metals, but those who understand steels and titaniums will have heard of it as an additive for its reinforcement in alloys or tools. Physically it is synonymous with hardness, and chemically, with colors.
Some chemists dare to describe it as a chameleon metal, capable of adopting a wide range of colors in its compounds; electronic property that resembles that of the metals manganese and chromium. In its native and pure state, it looks the same as other metals: silver, but with bluish hues. Once rusted, it looks as shown below.
In this image, the iridescence of the oxide is barely distinguishable, which depends on the finishes or surface of the metallic crystals. This oxide layer protects it from further oxidation and therefore corrosion.
Such resistance to corrosion, as well as thermal cracking, is provided to alloys when V atoms are added to them. All this, without raising its weight too much, since vanadium is not a heavy metal but a light one; unlike what many may think.
Its name derives from the Norse goddess Vanadís, from Scandinavia; however, it was discovered in Mexico, as part of the vanadinite mineral, Pb5[VO4]3Cl, of reddish crystals. The problem was that to obtain it from this mineral and many others, vanadium had to be transformed into a compound easier to reduce than its oxide, VtwoOR5 (which is reduced by calcium).
Other sources of vanadium lie in marine beings, or in crude oil, "imprisoned" within the petroporphyrins..
In solution, the colors that its compounds can have, depending on their oxidation state, are yellow, blue, dark green or violet. Vanadium not only stands out for these numbers or oxidation states (from -1 to +5), but for its ability to coordinate in different ways with biological environments.
The chemistry of vanadium is abundant, mysterious, and compared to other metals there is still much light that must be shed on it for its close understanding..
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Mexico has the honor of having been the country where this element was discovered. The mineralogist Andrés Manuel del Río, in 1801, analyzing a reddish mineral that he himself called brown lead (vanadinite, Pb5[VO4]3Cl), extracted some metallic oxides whose characteristics did not correspond to those of any element known at that time.
Thus, he first baptized this element with the name of 'Pancromo' due to the rich variety of colors of its compounds; then he renamed it 'Erythrono', from the Greek word erythronium, which means red.
Four years later, the French chemist Hippolyte Victor Collet Descotils, managed to get Del Río to retract his claims by suggesting that erythron was not a new element but chromium impurities. And it took more than twenty years for something to be known about this forgotten element discovered in Mexican soils..
In 1830 the Swiss chemist Nils Gabriel Sefström, discovered another new element in iron ores, which he called vanadium; name that derived from the Norse goddess Vanadís, in comparison of its beauty with the brilliant colors of the compounds of this metal.
That same year, the German geologist George William Featherstonhaugh, pointed out that vanadium and erythron were actually the same element; and although he wanted the name of the River to prevail by calling it 'Rionio', his proposal was not accepted.
To isolate vanadium it was necessary to reduce it from its minerals, and like scandium and titanium, this task was not easy due to its tenacious affinity for oxygen. It had to first be transformed into species that were relatively easily reduced; in the process, Berzelius obtained vanadium nitride in 1831, which he mistook for the native metal.
In 1867 the English chemist Henry Enfield Roscoe, achieved the reduction of vanadium (II) chloride, VCltwo, to metallic vanadium using hydrogen gas. However, the metal it produced was impure.
Finally, marking the beginning of the technological history of vanadium, a high purity sample was obtained by reducing the VtwoOR5 with metallic calcium. One of its first prominent uses was to make the chassis of the Ford Model T car..
In its pure form, it is a grayish metal with bluish overtones, soft and ductile. However, when it is covered with a layer of oxide (especially the product of a lighter), it takes on striking colors as if it were a crystal chameleon.
50.9415 g / mol
1910 ° C
3407 ° C
-6.0 g / mL, at room temperature
-5.5 g / mL, at the melting point, that is, it hardly melts.
21.5 kJ / mol
444 kJ / mol
Molar heat capacity
24.89 J / (mol K)
1 Pa at 2101 K (practically negligible even at high temperatures).
1.63 on the Pauling scale.
First: 650.9 kJ / mol (V+ gaseous)
Second: 1414 kJ / mol (Vtwo+ gaseous)
Third: 2830 kJ / mol (V3+ gaseous)
6.7
When heated it can release toxic fumes from VtwoOR5.
One of the main and notorious characteristics of vanadium is the colors of its compounds. When some of them are dissolved in acidic media, the solutions (mostly aqueous) exhibit colors that allow one to distinguish one number or oxidation state from another..
For example, the image above shows four test tubes with vanadium in different oxidation states. The one on the left, yellow, corresponds to V5+, specifically as cation VOtwo+. Then it is followed by the cation VOtwo+, with V4+, the color blue; cation V3+, dark green; and Vtwo+, purple or mauve.
When a solution consists of a mixture of compounds of V4+ and V5+, a bright green color is obtained (product of yellow with blue).
The V layertwoOR5 on vanadium protects it from reacting with strong acids, such as sulfuric or hydrochloric, strong bases, and in addition to corrosion caused by increased oxidation.
When heated above 660 ° C, vanadium oxidizes completely, looking like a yellow solid with iridescent sheen (depending on the angles of its surface). This orange-yellow oxide can be dissolved if nitric acid is added, which would return the vanadium to its silver color..
Almost all the vanadium atoms in the Universe (99.75% of them) are about the isotope 51V, while a very small portion (0.25%) corresponds to the isotope fiftyV. Hence it is not surprising that the atomic weight of vanadium is 50.9415 u (closer to 51 than 50).
The other isotopes are radioactive and synthetic, with half-lives (t1/2) ranging from 330 days (49V), 16 days (48V), a few hours or 10 seconds.
Vanadium atoms, V, are arranged in a body-centered cubic (bcc) crystal structure, the product of their metallic bond. Of the structures, this is the least dense, with its five valence electrons participating in the "sea of electrons", according to the electronic configuration:
[Ar] 3d3 4stwo
Thus, the three electrons of the 3d orbital, and the two of the 4s orbital, unite to transit a band formed by the overlapping of the valence orbitals of all the V atoms of the crystal; clearly, explanation based on band theory.
Because the V atoms are a little smaller than the metals to their left (scandium and titanium) in the periodic table, and given their electronic characteristics, their metallic bond is stronger; a fact that is reflected in its highest melting point and, therefore, with its more cohesive atoms.
According to computational studies, the bcc structure of vanadium is stable even under enormous pressures of 60 GPa. Once this pressure is exceeded, its crystal undergoes a transition to the rhombohedral phase, which remains stable up to 434 GPa; when the bcc structure reappears again.
The electron configuration of vanadium alone indicates that its atom is capable of losing up to five electrons. When it does, the noble gas argon becomes isoelectronic, and the existence of the cation V is assumed.5+.
Likewise, the loss of electrons can be gradual (depending on which species it is linked to), having positive oxidation numbers that vary from +1 to +5; therefore, in their compounds the existence of the respective cations V is assumed+, Vtwo+ and so on.
Vanadium can also gain electrons, transforming into a metallic anion. Its negative oxidation numbers are: -1 (V-) and -3 (V3-). The electron configuration of the V3- it is:
[Ar] 3d6 4stwo
Although it lacks four electrons to complete the filling of the 3d orbitals, V is more stable energetically3- that the V7-, which in theory would need extremely electropositive species (to give it their electrons).
Vanadium provides mechanical, thermal and vibrational resistance, as well as hardness to the alloys to which it is added. For example, as ferrovanadium (iron and vanadium alloy), or vanadium carbide, it is added together with other metals in steel or in titanium alloys.
In this way, very hard and at the same time light materials are created, useful to be used as tools (drills and wrenches), gears, automobile or aircraft parts, turbines, bicycles, jet engines, knives, dental implants, etc..
Also, its alloys with gallium (V3Ga) are superconducting and are used to make magnets. And also, given their low reactivity, vanadium alloys are used for pipes where corrosive chemical reagents run..
Vanadium is part of redox batteries, VRB (for its acronym in English: Vanadium Redox Batteries). These can be used to promote the generation of electricity from solar and wind energy, as well as batteries in electric vehicles.
The VtwoOR5 It is used to give glass and ceramics a golden color. On the other hand, its presence in some minerals makes them greenish, as happens with emeralds (and thanks to other metals as well).
The VtwoOR5 It is also a catalyst used for the synthesis of sulfuric acid and maleic anhydride acid. Mixed with other metal oxides, it catalyzes other organic reactions, such as the oxidation of propane and propylene to acrolein and acrylic acid, respectively..
Drugs consisting of vanadium complexes have been considered as possible and potential candidates for the treatment of diabetes and cancer..
It seems ironic that vanadium, being its colorful and toxic compounds, its ions (VO+, VOtwo+ and VO43-, mostly) in traces they are beneficial and essential for living beings; especially those of marine habitats.
The reasons are centered on its oxidation states, with how many ligands in the biological environment it coordinates (or interacts), in the analogy between the vanadate and phosphate anion (VO43- and PO43-), and in other factors studied by bioinorganic chemists.
Vanadium atoms can then interact with those atoms belonging to enzymes or proteins, either with four (coordination tetrahedron), five (square pyramid or other geometries) or six. If when this occurs a favorable reaction for the body is triggered, it is said that vanadium exerts pharmacological activity.
For example, there are the haloperoxidases: enzymes that can use vanadium as a cofactor. There are also vanabins (in the vanadocyte cells of tunicates), phosphorylases, nitrogenases, transferins and serum albumins (of mammals), capable of interacting with this metal.
An organic molecule or vanadium coordination complex called amavadin, is present in the bodies of certain fungi, such as Amanita muscaria (lower image).
And finally, in some complexes, vanadium may be contained in a heme group, as is the case with iron in hemoglobin..
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