Group 5 is agroup of elements in theperiodic table. Group 5 containsvanadium (V),niobium (Nb),tantalum (Ta) anddubnium (Db).^[1] This group lies in thed-block of the periodic table. This group is sometimes called thevanadium group orvanadium family after its lightest member; however, the group itself has not acquired atrivial name because it belongs to the broader grouping of thetransition metals.

↓ Period
4	Vanadium (V) 23Transition metal
5	Niobium (Nb) 41Transition metal
6	Tantalum (Ta) 73Transition metal
7	Dubnium (Db) 105Transition metal
Legend primordial element synthetic element

As is typical for early transition metals, niobium and tantalum have only the groupoxidation state of +5 as a major one, and are quite electropositive (it is easy to donate electrons) and have a less rich coordination chemistry (the chemistry of metallic ions bound with molecules). Due to the effects of thelanthanide contraction, the decrease in ionic radii in thelanthanides, they are very similar in properties. Vanadium is somewhat distinct due to its smaller size: it has well-defined +2, +3 and +4 states as well (although +5 is more stable).

The lighter three Group 5 elements occur naturally and share similar properties; all three are hardrefractory metals under standard conditions. The fourth element,dubnium, has been synthesized in laboratories, but it has not been found occurring in nature, with half-life of the most stable isotope, dubnium-268, being only 16 hours, and other isotopes even moreradioactive.

Group 5 is the new IUPAC name for this group; the old style name wasgroup VB in the old US system (CAS) orgroup VA in the European system (old IUPAC). Group 5 must not be confused with the group with the old-style group crossed names of eitherVA (US system, CAS) orVB (European system, old IUPAC); that group is now called thepnictogens or group 15.^[2]

Vanadium wasdiscovered in 1801 by the Spanish mineralogistAndrés Manuel del Río. Del Río extracted the element from a sample of Mexican "brown lead" ore, later namedvanadinite. He found that its salts exhibit a wide variety of colors, and as a result he named the elementpanchromium (Greek: παγχρώμιο "all colors"). Later, Del Río renamed the elementerythronium (Greek: ερυθρός "red") because most of the salts turned red upon heating. In 1805, French chemistHippolyte Victor Collet-Descotils, backed by del Río's friend BaronAlexander von Humboldt, incorrectly declared that del Río's new element was an impure sample ofchromium. Del Río accepted Collet-Descotils' statement and retracted his claim.^[3]

In 1831 Swedish chemistNils Gabriel Sefström rediscovered the element in a new oxide he found while working withiron ores. Later that year,Friedrich Wöhler confirmed del Río's earlier work.^[4] Sefström chose a name beginning with V, which had not yet been assigned to any element. He called the elementvanadium afterOld NorseVanadís (another name for theNorseVanir goddessFreyja, whose attributes include beauty and fertility), because of the many beautifully coloredchemical compounds it produces.^[4] In 1831, the geologistGeorge William Featherstonhaugh suggested that vanadium should be renamedrionium after del Río, but this suggestion was not followed.^[5]

Niobium wasidentified by English chemistCharles Hatchett in 1801.^[6][7][8] He found a new element in a mineral sample that had been sent to England fromConnecticut, United States in 1734 by John Winthrop F.R.S. (grandson ofJohn Winthrop the Younger) and named the mineralcolumbite and the new elementcolumbium afterColumbia,^[9] the poetic name for the United States.^[10][11][12] However, after the 15th Conference of the Union of Chemistry in Amsterdam in 1949, the name niobium was chosen for element 41.^[13] Thecolumbium discovered by Hatchett was probably a mixture of the new element with tantalum, which was first discovered in 1802 byAnders Gustav Ekeberg.^[10]

Subsequently, there was considerable confusion^[14] over the difference between columbium (niobium) and the closely related tantalum. In 1809, English chemistWilliam Hyde Wollaston compared the oxides derived from both columbium—columbite, with a density 5.918 g/cm³, and tantalum—tantalite, with a density over 8 g/cm³, and concluded that the two oxides, despite the significant difference in density, were identical; thus he kept the name tantalum.^[14] This conclusion was disputed in 1846 by German chemistHeinrich Rose, who argued that there were two different elements in the tantalite sample, and named them after children ofTantalus:niobium (fromNiobe) andpelopium (fromPelops).^[15][16] This confusion arose from the minimal observed differences between tantalum and niobium. The claimed new elementspelopium,ilmenium, anddianium^[17] were in fact identical to niobium or mixtures of niobium and tantalum.^[18] Pure tantalum was not produced until 1903.^[19]

The last element of the group,dubnium, does not occur naturally and so must be synthesized in a laboratory. The first reported detection was by a team at theJoint Institute for Nuclear Research (JINR), which in 1968 had produced the new element by bombarding anamericium-243 target with a beam ofneon-22 ions, and reported 9.4 MeV (with a half-life of 0.1–3 seconds) and 9.7 MeV (t_1/2 > 0.05 s)alpha activities followed by alpha activities similar to those of either²⁵⁶103 or²⁵⁷103. Based on prior theoretical predictions, the two activity lines were assigned to²⁶¹105 and²⁶⁰105, respectively.^[20]

After observing the alpha decays of element 105, the researchers aimed to observe thespontaneous fission (SF) of the element and study the resulting fission fragments. They published a paper in February 1970, reporting multiple examples of two such activities, with half-lives of 14 ms and2.2±0.5 s. They assigned the former activity to^242mfAm^[a] and ascribed the latter activity to an isotope of element 105. They suggested that it was unlikely that this activity could come from a transfer reaction instead of element 105, because the yield ratio for this reaction was significantly lower than that of the^242mfAm-producing transfer reaction, in accordance with theoretical predictions. To establish that this activity was not from a (²²Ne,xn) reaction, the researchers bombarded a²⁴³Am target with¹⁸O ions; reactions producing²⁵⁶103 and²⁵⁷103 showed very little SF activity (matching the established data), and the reaction producing heavier²⁵⁸103 and²⁵⁹103 produced no SF activity at all, in line with theoretical data. The researchers concluded that the activities observed came from SF of element 105.^[20]

JINR then attempted an experiment to create element 105, published in a report in May 1970. They claimed that they had synthesized more nuclei of element 105 and that the experiment confirmed their previous work. According to the paper, the isotope produced by JINR was probably²⁶¹105, or possibly²⁶⁰105.^[20] This report included an initial chemical examination: the thermal gradient version of the gas-chromatography method was applied to demonstrate that the chloride of what had formed from the SF activity nearly matched that ofniobium pentachloride, rather thanhafnium tetrachloride. The team identified a 2.2-second SF activity in a volatile chloride portraying eka-tantalum properties, and inferred that the source of the SF activity must have been element 105.^[20]

In June 1970, JINR made improvements on their first experiment, using a purer target and reducing the intensity of transfer reactions by installing acollimator before the catcher. This time, they were able to find 9.1 MeV alpha activities with daughter isotopes identifiable as either²⁵⁶103 or²⁵⁷103, implying that the original isotope was either²⁶⁰105 or²⁶¹105.^[20]

Acontroversy erupted on who had discovered the element, which each group suggesting its own name: the Dubna group named the elementnielsbohrium afterNiels Bohr, while the Berkeley group named ithahnium afterOtto Hahn.^[21] Eventually a joint working party ofIUPAC andIUPAP, the Transfermium Working Group, decided that credit for the discovery should be shared. After various compromises were attempted, where element 105 was calledkurchatovium,joliotium andhahnium, in 1997 IUPAC officially named the element dubnium after Dubna,^[22][19] andnielsbohrium was eventually simplified tobohrium and used forelement 107.^[23][24]

Like other groups, the members of this family show patterns in itselectron configuration, especially the outermost shells. (The expected 4d³ 5s² configuration for niobium is a very low-lying excited state at about 0.14 eV.)^[25]

Most of the chemistry has been observed only for the first three members of the group (the chemistry of dubnium is not very established, but what is known appears to match expectations for a heavier congener of tantalum). All the elements of the group are reactive metals with a high melting points (1910 °C, 2477 °C, 3017 °C). The reactivity is not always obvious due to the rapid formation of a stable oxide layer, which prevents further reactions, similarly to trends in group 3 or group 4. The metals form different oxides: vanadium formsvanadium(II) oxide,vanadium(III) oxide,vanadium(IV) oxide andvanadium(V) oxide, niobium formsniobium(II) oxide,niobium(IV) oxide andniobium(V) oxide, but out of tantalum oxides onlytantalum(V) oxide is characterized. Metal(V) oxides are generally nonreactive and act like acids rather than bases, but the lower oxides are less stable. They, however, have some unusual properties for oxides, such as high electric conductivity.^[26]

All three elements form variousinorganic compounds, generally in the oxidation state of +5. Lower oxidation states are also known, but in all elements other than vanadium,^[27] they are less stable, decreasing in stability with atomic mass increase.^[28]

Vanadium forms oxides in the +2, +3, +4 and +5oxidation states, formingvanadium(II) oxide (VO),vanadium(III) oxide (V₂O₃),vanadium(IV) oxide (VO₂) andvanadium(V) oxide (V₂O₅). Vanadium(V) oxide or vanadium pentoxide is the most common, being precursor to most alloys and compounds of vanadium, and is also a widely used industrial catalyst.^[29]

Niobium forms oxides in the oxidation states +5 (Nb₂O₅),^[30] +4 (NbO₂), and the rarer oxidation state, +2 (NbO).^[31] Most common is the pentoxide, also being precursor to almost all niobium compounds and alloys.^[26][32]

Tantalum pentoxide (Ta₂O₅) is the most important compound from the perspective of applications. Oxides of tantalum in lower oxidation states are numerous, including manydefect structures, and are lightly studied or poorly characterized.^[31]

In aqueous solution, vanadium(V) forms an extensive family ofoxyanions as established by⁵¹V NMR spectroscopy.^[33] The interrelationships in this family are described by thepredominance diagram, which shows at least 11 species, depending on pH and concentration.^[34] The tetrahedral orthovanadate ion,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 inprotein crystallography^[35] to study thebiochemistry of phosphate.^[36] Beside that, this anion also has been shown to interact with activity of some specific enzymes.^[37][38] The tetrathiovanadate [VS₄]³⁻ is analogous to the orthovanadate ion.^[39]

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 thedichromate ion. As the pH is reduced, further protonation and condensation topolyvanadates 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 2–4decavanadate predominates, though its formation from orthovanadate is optimized at pH 4–7, represented by this reaction:^[40]

10 Na₃[VO₄] + 24 HOAc → Na₆[V₁₀O₂₈] + 12 H₂O + 24 NaOAc

In decavanadate, each V(V) center is surrounded by six oxideligands.^[26] 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 < 2, [VO₂(H₂O)₄]⁺ is the predominant species, while the oxide V₂O₅ precipitates from solution at high concentrations.^[41] The oxide is formally theacid anhydride of vanadic acid. The structures of manyvanadate compounds have been determined by X-ray crystallography.^[42]

Vanadium(V) forms various peroxo complexes, most notably in the active site of the vanadium-containingbromoperoxidase 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.^[44][45]

Niobates are generated by dissolving the pentoxide inbasichydroxide solutions or by melting it in alkali metal oxides. Examples arelithium niobate (LiNbO₃) and lanthanum niobate (LaNbO₄). In the lithium niobate is a trigonally distortedperovskite-like structure, whereas the lanthanum niobate contains loneNbO³⁻
₄ ions.^[26]

Tantalates, compounds containing [TaO₄]³⁻ or [TaO₃]⁻ are numerous.Lithium tantalate (LiTaO₃) adopts a perovskite structure.Lanthanum tantalate (LaTaO₄) contains isolatedTaO³⁻
₄ tetrahedra.^[26]

Twelve binaryhalides, compounds with the formula VX_n (n=2...5), are known. VI₄, VCl₅, VBr₅, and VI₅ do not exist or are extremely unstable; the only known pure V⁵⁺ halide compound isVF₅.^[46] In combination with other reagents,VCl₄ is used as a catalyst for polymerization ofdienes. Like all binary halides, those of vanadium areLewis acidic, especially those of V(IV) and V(V). Many of the halides form octahedral complexes with the formula VX_nL_6−n (X= halide; L= other ligand).^[47][48]

Many vanadiumoxyhalides (formula VO_mX_n) are known.^[49] The oxytrichloride and oxytrifluoride (VOCl₃ andVOF₃) are the most widely studied. Akin to POCl₃, they are volatile, adopt tetrahedral structures in the gas phase, and are Lewis acidic.^[50]

Niobium forms halides in the oxidation states of +5 and +4 as well as diversesubstoichiometric compounds.^[26][51] The pentahalides (NbX
₅) feature octahedral Nb centres. Niobium pentafluoride (NbF₅) is a white solid with a melting point of 79.0 °C andniobium pentachloride (NbCl₅) is yellow (see image at left) with a melting point of 203.4 °C. Both arehydrolyzed to give oxides and oxyhalides, such asNbOCl₃. The pentachloride is a versatile reagent used to generate theorganometallic compounds, such asniobocene dichloride ((C
₅H
₅)
₂NbCl
₂).^[52] The tetrahalides (NbX
₄) are dark-coloured polymers with Nb-Nb bonds; for example, the blackhygroscopic niobium tetrafluoride (NbF₄)^[53] and dark violet niobium tetrachloride (NbCl₄).^[54]

Anionic halide compounds of niobium are well known, owing in part to theLewis acidity of the pentahalides. The most important is [NbF₇]²⁻, an intermediate in the separation of Nb and Ta from the ores.^[55] This heptafluoride tends to form the oxopentafluoride more readily than does the tantalum compound. Other halide complexes include octahedral [NbCl₆]⁻:

Nb₂Cl₁₀ + 2 Cl⁻ → 2 [NbCl₆]⁻

As with other metals with low atomic numbers, a variety of reduced halide cluster ions is known, the prime example being [Nb₆Cl₁₈]⁴⁻.^[31]

Tantalum halides span the oxidation states of +5, +4, and +3.Tantalum pentafluoride (TaF₅) is a white solid with a melting point of 97.0 °C. The anion [TaF₇]^2- is used for its separation from niobium.^[55] The chlorideTaCl
₅, which exists as a dimer, is the main reagent in synthesis of new Ta compounds. It hydrolyzes readily to anoxychloride. The lower halidesTaX
₄ andTaX
₃, feature Ta-Ta bonds.^[26][51]

The trends in group 5 follow those of the other early d-block groups and reflect the addition of a filled f-shell into the core in passing from the fifth to the sixth period. All the stable members of the group are silvery-bluerefractory metals, though impurities ofcarbon,nitrogen, and oxygen make them brittle.^[28] They all crystallize in thebody-centered cubic structure at room temperature,^[56] and dubnium is expected to do the same.^[57]

The table below is a summary of the key physical properties of the group 5 elements. The question-marked value is predicted.^[58]

Vanadium is an average-hard,ductile, steel-blue metal. It is electricallyconductive and thermallyinsulating. Some sources describe vanadium as "soft", perhaps because it is ductile,malleable, and notbrittle.^[61][62] Vanadium is harder than most metals and steels (seeHardnesses of the elements (data page) andiron). It has good resistance tocorrosion and it is stable againstalkalis andsulfuric andhydrochloric acids.^[26] It isoxidized in air at about 933 K (660 °C, 1220 °F), although an oxidepassivation layer forms even at room temperature.^[63]

Niobium is alustrous, grey,ductile,paramagneticmetal in group 5 of theperiodic table (see table), with an electron configuration in the outermostshells atypical for group 5. Similarly atypical configurations occur in the neighborhood ofruthenium (44) andrhodium (45).^[64]

Although it is thought to have abody-centered cubic crystal structure from absolute zero to its melting point, high-resolution measurements of the thermal expansion along the three crystallographic axes reveal anisotropies which are inconsistent with a cubic structure.^[65]

Niobium becomes asuperconductor atcryogenic temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors at 9.2 K.^[66] Niobium has the greatestmagnetic penetration depth of any element.^[66] In addition, it is one of the three elementalType II superconductors, along withvanadium andtechnetium. The superconductive properties are strongly dependent on the purity of the niobium metal.^[67]

When very pure, it is comparatively soft and ductile, but impurities make it harder.^[68]

The metal has a lowcapture cross-section for thermalneutrons;^[69] thus it is used in the nuclear industries where neutron transparent structures are desired.^[70]

Tantalum is dark (blue-gray),^[71] dense, ductile, very hard, easily fabricated, and highly conductive of heat and electricity. The metal is renowned for its resistance tocorrosion byacids; in fact, at temperatures below 150 °C tantalum is almost completely immune to attack by the normally aggressiveaqua regia. It can be dissolved withhydrofluoric acid or acidic solutions containing thefluoride ion andsulfur trioxide, as well as with a solution ofpotassium hydroxide. Tantalum's high melting point of 3017 °C (boiling point 5458 °C) is exceeded among the elements only bytungsten,^[72]rhenium^[73]osmium,^[74] andcarbon.^[75]

Tantalum exists in two crystalline phases, alpha and beta. The alpha phase is relativelyductile and soft; it hasbody-centered cubic structure (space groupIm3m, lattice constanta = 0.33058 nm),Knoop hardness 200–400 HN and electrical resistivity 15–60 μΩ⋅cm. The beta phase is hard and brittle; its crystal symmetry istetragonal (space groupP42/mnm,a = 1.0194 nm,c = 0.5313 nm), Knoop hardness is 1000–1300 HN and electrical resistivity is relatively high at 170–210 μΩ⋅cm. The beta phase is metastable and converts to the alpha phase upon heating to 750–775 °C. Bulk tantalum is almost entirely alpha phase, and the beta phase usually exists as thin films^[76] obtained by magnetronsputtering,chemical vapor deposition orelectrochemical deposition from aeutectic molten salt solution.^[77]

A direct relativistic effect is that as the atomic numbers of elements increase, the innermost electrons begin to revolve faster around the nucleus as a result of an increase ofelectromagnetic attraction between an electron and a nucleus. Similar effects have been found for the outermost sorbitals (and p_1/2 ones, though in dubnium they are not occupied): for example, the 7s orbital contracts by 25% in size and is stabilized by 2.6 eV.^[58]

A more indirect effect is that the contracted s and p_1/2 orbitalsshield the charge of the nucleus more effectively, leaving less for the outer d and f electrons, which therefore move in larger orbitals. Dubnium is greatly affected by this: unlike the previous group 5 members, its 7s electrons are slightly more difficult to extract than its 6d electrons.^[58]

Another effect is thespin–orbit interaction, particularly spin–orbit splitting, which splits the 6d subshell—theazimuthal quantum number ℓ of a d shell is 2—into two subshells, with four of the ten orbitals having their ℓ lowered to 3/2 and six raised to 5/2. All ten energy levels are raised; four of them are lower than the other six. (The three 6d electrons normally occupy the lowest energy levels, 6d_3/2.)^[58]

A single ionized atom of dubnium (Db⁺) should lose a 6d electron compared to a neutral atom; the doubly (Db²⁺) or triply (Db³⁺) ionized atoms of dubnium should eliminate 7s electrons, unlike its lighter homologs. Despite the changes, dubnium is still expected to have five valence electrons; 7p energy levels have not been shown to influence dubnium and its properties. As the 6d orbitals of dubnium are more destabilized than the 5d ones of tantalum, and Db³⁺ is expected to have two 6d, rather than 7s, electrons remaining, the resulting +3 oxidation state is expected to be unstable and even rarer than that of tantalum. The ionization potential of dubnium in its maximum +5 oxidation state should be slightly lower than that of tantalum and the ionic radius of dubnium should increase compared to tantalum; this has a significant effect on dubnium's chemistry.^[58]

Atoms of dubnium in the solid state should arrange themselves in abody-centered cubic configuration, like the previous group 5 elements.^[57] The predicted density of dubnium is 21.6 g/cm³.^[59]

There are 160 parts per million of vanadium in the Earth's crust, making it the19th most abundant element.Soil contains on average 100 parts per million of vanadium, andseawater contains 1.5 parts per billion of vanadium. A typical human contains 285 parts per billion of vanadium. Over 60 vanadium ores are known, includingvanadinite,patronite, andcarnotite.^[19] There are 20 parts per million of niobium in the Earth's crust, making it the 33rd most abundant element there. Soil contains on average 24 parts per million of niobium, and seawater contains 900 parts perquadrillion of niobium. A typical human contains 21 parts per billion of niobium. Niobium is in the mineralscolumbite andpyrochlore.^[19] There are 2 parts per million of tantalum in the Earth's crust, making it the 51st most abundant element there. Soil contains on average 1 to 2 parts per billion of tantalum, and seawater contains 2 parts per trillion of tantalum. A typical human contains 2.9 parts per billion of tantalum. Tantalum is found in the mineralstantalite and pyrochlore.^[19] Dubnium does not occur naturally in the Earth's crust, as it has no stableisotopes.^[78]

Vanadium metal is obtained by a multistep process that begins with roasting crushed ore withNaCl orNa₂CO₃ at about 850 °C to givesodium metavanadate (NaVO₃). An aqueous extract of this solid is acidified to produce "red cake", a polyvanadate salt, which is reduced withcalcium metal. As an alternative for small-scale production, vanadium pentoxide is reduced withhydrogen ormagnesium. Many other methods are also used, in all of which vanadium is produced as abyproduct of other processes.^[79] Purification of vanadium is possible by thecrystal bar process developed byAnton Eduard van Arkel andJan Hendrik de Boer in 1925. It involves the formation of the metal iodide, in this examplevanadium(III) iodide, and the subsequent decomposition to yield pure metal:^[80]

2 V + 3 I₂ ⇌ 2 VI₃

Most vanadium is used as a component of asteel alloy calledferrovanadium. Ferrovanadium is produced directly by reducing a mixture of vanadium oxide, iron oxides and iron in an electric furnace. The vanadium ends up inpig iron produced from vanadium-bearing magnetite. Depending on the ore used, the slag contains up to 25% of vanadium.^[79]

Approximately 70000tonnes of vanadium ore are produced yearly, with 25000 t of vanadium ore being produced in Russia, 24000 inSouth Africa, 19000 in China, and 1000 inKazakhstan. 7000 t of vanadium metal are produced each year. It is impossible to obtain vanadium by heating its ore with carbon. Instead, vanadium is produced by heatingvanadium oxide with calcium in apressure vessel. Very high-purity vanadium is produced from a reaction ofvanadium trichloride with magnesium.^[19]

After the separation from the other minerals, themixed oxides of tantalumTa₂O₅ and niobiumNb₂O₅ are obtained. To produce niobium, the first step in the processing is the reaction of the oxides withhydrofluoric acid:^[55]

Ta₂O₅ + 14 HF → 2 H₂[TaF₇] + 5 H₂O

Nb₂O₅ + 10 HF → 2 H₂[NbOF₅] + 3 H₂O

The first industrial scale separation, developed bySwisschemistde Marignac, exploits the differingsolubilities of the complex niobium and tantalumfluorides, dipotassium oxypentafluoroniobate monohydrate (K₂[NbOF₅]·H₂O) and dipotassium heptafluorotantalate (K₂[TaF₇]) in water. Newer processes use the liquid extraction of the fluorides fromaqueous solution byorganic solvents likecyclohexanone.^[55] The complex niobium and tantalum fluorides are extracted separately from theorganic solvent with water and either precipitated by the addition ofpotassium fluoride to produce a potassium fluoride complex, or precipitated withammonia as the pentoxide:^[26]

H₂[NbOF₅] + 2 KF → K₂[NbOF₅]↓ + 2 HF

Followed by:

2 H₂[NbOF₅] + 10 NH₄OH → Nb₂O₅↓ + 10 NH₄F + 7 H₂O

Several methods are used for thereduction to metallic niobium. Theelectrolysis of amolten mixture ofK₂[NbOF₅] andsodium chloride is one; the other is the reduction of the fluoride withsodium. With this method, a relatively high purity niobium can be obtained. In large scale production,Nb₂O₅ is reduced with hydrogen or carbon.^[26] In thealuminothermic reaction, a mixture ofiron oxide and niobium oxide is reacted withaluminium:

3 Nb₂O₅ + Fe₂O₃ + 12 Al → 6 Nb + 2 Fe + 6 Al₂O₃

Small amounts of oxidizers likesodium nitrate are added to enhance the reaction. The result isaluminium oxide andferroniobium, an alloy of iron and niobium used in steel production.^[83][84] Ferroniobium contains between 60 and 70% niobium.^[85] Without iron oxide, the aluminothermic process is used to produce niobium. Further purification is necessary to reach the grade forsuperconductive alloys.Electron beam melting under vacuum is the method used by the two major distributors of niobium.^[51][86]

As of 2013^[update],CBMM from Brazil controlled 85 percent of the world's niobium production.^[87] TheUnited States Geological Survey estimates that the production increased from 38,700 tonnes in 2005 to 44,500 tonnes in 2006.^[88][89] Worldwide resources are estimated to be 4.4 million tonnes.^[89] During the ten-year period between 1995 and 2005, the production more than doubled, starting from 17,800 tonnes in 1995.^[90] Between 2009 and 2011, production was stable at 63,000 tonnes per year,^[91] with a slight decrease in 2012 to only 50,000 tonnes per year.^[92]

70,000 tonnes of tantalum ore are produced yearly. Brazil produces 90% of tantalum ore, with Canada, Australia, China, andRwanda also producing the element. The demand for tantalum is around 1,200 tonnes per year.^[19]

Dubnium is produced synthetically by bombardingactinides with lighter elements.^[19] To date, no experiments in asupercollider have been conducted tosynthesize the next member of the group, either unpentseptium (Ups) or unpentennium (Upe). As unpentseptium and unpentennium are both lateperiod 8 elements, it is unlikely that these elements will be synthesized in the near future; current attempts have only been made on elements up to atomic number 127.^[93]

Vanadium's main application is in alloys, such asvanadium steel. Vanadium alloys are used insprings,tools,jet engines,armor plating, andnuclear reactors.Vanadium oxide gives ceramics a golden color, and other vanadium compounds are used ascatalysts to producepolymers.^[19]

Small amounts of niobium are added tostainless steel to improve its quality. Niobium alloys are also used in rocket nozzles because of niobium's highcorrosion resistance.^[19]

Tantalum has four main types of applications. Tantalum is added into objects exposed to high temperatures, inelectronic devices, insurgical implants, and for handling corrosive substances.^[19]

Dubnium has no applications due to the difficulty of its synthesis and the very short half-lives of even its longest-lived isotopes.^[94]

Out of the group 5 elements, only vanadium has been identified as playing a role in the biological chemistry of living systems, but even it plays a very limited role inbiology, and is more important in ocean environments than on land.^[50]

Vanadium, essential toascidians andtunicates asvanabins, has been known in theblood cells ofAscidiacea (sea squirts) since 1911,^[95][96] in concentrations of vanadium in their blood more than 100 times higher than the concentration of vanadium in the seawater around them. Several species of macrofungi accumulate vanadium (up to 500 mg/kg in dry weight).^[97] Vanadium-dependentbromoperoxidase generates organobromine compounds in a number of species of marinealgae.^[98]

Rats andchickens are also known to require vanadium in very small amounts and deficiencies result in reduced growth and impairedreproduction.^[99] Vanadium is a relatively controversialdietary supplement, primarily for increasinginsulin sensitivity^[100] andbody-building.Vanadyl sulfate may improve glucose control in people withtype 2 diabetes.^[101] In addition, decavanadate and oxovanadates are species that potentially have many biological activities and that have been successfully used as tools in the comprehension of several biochemical processes.^[102]

Pure vanadium is not known to be toxic. However,vanadium pentoxide causes severe irritation of the eyes, nose, and throat.^[19] TetravalentVOSO₄ has been reported to be at least 5 times more toxic than trivalent V₂O₃.^[103] TheOccupational Safety and Health Administration has set an exposure limit of 0.05 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.^[104] TheNational Institute for Occupational Safety and Health 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.^[104] Vanadium compounds are poorly absorbed through the gastrointestinal system. Inhalation of vanadium and vanadium compounds results primarily in adverse effects on the respiratory system.^{[105][106][107]} 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,^[108][109] liver,^[110] neurological development,^[111] and other organs^[112] in rats.

There is little evidence that vanadium or vanadium compounds are reproductive toxins orteratogens. Vanadium pentoxide was reported to be carcinogenic in male rats and in male and female mice by inhalation in an NTP study,^[106] although the interpretation of the results has recently been disputed.^[113] The carcinogenicity of vanadium has not been determined by theUnited States Environmental Protection Agency.^[114] Vanadium traces indiesel fuels are the main fuel component inhigh temperature corrosion. During combustion, vanadium oxidizes and reacts with sodium and sulfur, yieldingvanadate compounds with melting points as low as 530 °C, which attack thepassivation layer on steel and render it susceptible to corrosion. The solid vanadium compounds also abrade engine components.^[115][116]

Niobium has no known biological role. While niobium dust is an eye and skin irritant^[19] and a potential fire hazard, elemental niobium on a larger scale is physiologically inert (and thus hypoallergenic) and harmless. It is often used in jewelry and has been tested for use in some medical implants.^[117][118] Niobium and its compounds thought to be slightly toxic. Short- and long-term exposure to niobates and niobium chloride, two water-soluble chemicals, have been tested in rats. Rats treated with a single injection of niobium pentachloride or niobates show amedian lethal dose (LD₅₀) between 10 and 100 mg/kg.^{[119][120][121]} For oral administration the toxicity is lower; a study with rats yielded a LD₅₀ after seven days of 940 mg/kg.^[119]

Compounds containing tantalum are rarely encountered in the laboratory, and it and its compounds rarely cause injury, and when they do, the injuries are normally rashes.^[19] The metal is highlybiocompatible^[122] and is used for bodyimplants andcoatings, therefore attention may be focused on other elements or the physical nature of thechemical compound.^[123] People can be exposed to tantalum in the workplace by breathing it in, skin contact, or eye contact. TheOccupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for tantalum exposure in the workplace as 5 mg/m³ over an 8-hour workday. TheNational Institute for Occupational Safety and Health (NIOSH) has set arecommended exposure limit of 5 mg/m³ over an 8-hour workday and a short-term limit of 10 mg/m³. At levels of 2500 mg/m³, tantalum isimmediately dangerous to life and health.^[124]

• Greenwood, N (2003). "Vanadium to dubnium: from confusion through clarity to complexity".Catalysis Today.78 (1–4):5–11.doi:10.1016/S0920-5861(02)00318-8.