Which group has Valency of 5?

Question:

Which element below has five valence electrons?

a. Si

b. Se

c. S

d. I

e. Sb

The valence electrons are present in an outermost shell of an atom that can be involved in the formation of a chemical bonds. Elements belong to different group has different number of valence electrons.

Answer and Explanation:

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The Periodic Table: Properties of Groups and Periods

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Chapter 3 / Lesson 1

Learn about the organization of the periodic table into groups and periods and how these differ. Also learn the history of the periodic table and its properties.

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Group 5 in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson group 4 ←    → group 6
IUPAC group number 5 Name by element vanadium group CAS group number (US, pattern A-B-A) VB old IUPAC number (Europe, pattern A-B) VA
↓ Period
4	Vanadium (V) 23 Transition metal
5	Niobium (Nb) 41 Transition metal
6	Tantalum (Ta) 73 Transition metal
7	Dubnium (Db) 105 Transition metal
Legend primordial element synthetic element Atomic number color: black=solid
v t e

Group 5 (by IUPAC style) 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. This group is sometimes called the vanadium group or vanadium family after its lightest member; however, the group itself has not acquired a trivial name because it belongs to the broader grouping of the transition metals.

As is typical for early transition metals, niobium and tantalum have only the group oxidation state of +5 as a major one, and are quite electropositive and have a less rich coordination chemistry. Due to the effects of the lanthanide contraction, 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 hard refractory 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 29 hours, and other isotopes even more radioactive. To date, no experiments in a supercollider have been conducted to synthesize the next member of the group, either unpentseptium (Ups) or unpentennium (Upe). As unpentseptium and unpentennium are both late period 8 elements it is unlikely that these elements will be synthesized in the near future.

History[edit]

Vanadium was discovered by Andrés Manuel del Río, a Spanish-born Mexican mineralogist, in 1801 in the mineral vanadinite. After other chemists rejected his discovery of erythronium he retracted his claim.[1]It was later named after Vanadis, the Scandinavian goddess of love.

Niobium was discovered by the English chemist Charles Hatchett in 1801.[2], who named it columbium.[3] However, after the 15th Conference of the Union of Chemistry in Amsterdam in 1949, the name niobium was chosen for element 41,[4] after Niobe, a figure from Greek mythology.

Tantalum was first discovered in 1802 by Anders Gustav Ekeberg. However, it was thought to be identical to niobium until 1846, when Heinrich Rose proved that the two elements were different. Pure tantalum was not produced until 1903.[5] It is named after Tantalus, a figure from Greek mythology.

Dubnium was first produced in 1968 at the Joint Institute for Nuclear Research by bombarding americium-243 with neon-22 and was again produced at the Lawrence Berkeley Laboratory in 1970. The names "neilsbohrium" and "joliotium" were proposed for the element, but in 1997, the IUPAC decided to name the element dubnium, after Dubna, Russia.[5]

Chemical properties[edit]

Like other groups, the members of this family show patterns in its electron configuration, especially the outermost shells, though niobium curiously does not follow the trend:

Most of the chemistry has been observed only for the first three members of the group (the chemistry of dubnium is not very established, and therefore the rest of this section deals only with vanadium, niobium, and 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 forms vanadium(II) oxide, vanadium(III) oxide, vanadium(IV) oxide and vanadium(V) oxide, niobium forms niobium(II) oxide, niobium(IV) oxide and niobium(V) oxide, but out of tantalum oxides only tantalum(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.[6]

All three elements form various inorganic compounds, generally in the oxidation state of +5. Lower oxidation states are also known, but they are less stable, decreasing in stability with atomic mass increase.

Compounds[edit]

Oxides[edit]

Vanadium forms oxides in the +2, +3, +4 and +5 oxidation states, forming vanadium(II) oxide (VO), vanadium(III) oxide (V2O3, vanadium(IV) oxide (VO2) and vanadium(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.[7]

Niobium forms oxides in the oxidation states +5 (Nb2O5),[8] +4 (NbO2), and the rarer oxidation state, +2 (NbO).[9] Most common is the pentoxide, also being precursor to almost all niobium compounds and alloys.[6][10]

Tantalum pentoxide (Ta2O5) is the most important compound from the perspective of applications. Oxides of tantalum in lower oxidation states are numerous, including many defect structures, and are lightly studied or poorly characterized.[11]

Oxyanions[edit]

In aqueous solution, vanadium(V) forms an extensive family of oxyanions as established by 51V NMR spectroscopy.[12] The interrelationships in this family are described by the predominance diagram, which shows at least 11 species, depending on pH and concentration.[13] 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 in protein crystallography[14] to study the biochemistry of phosphate.[15] Beside that, this anion also has been shown to interact with activity of some specific enzymes.[16][17] The tetrathiovanadate [VS4]3− is analogous to the orthovanadate ion.[18]

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.[6] 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. The oxide is formally the acid anhydride of vanadic acid. The structures of many vanadate compounds have been determined by X-ray crystallography.

The Pourbaix diagram for vanadium in water, which shows the redox potentials between various vanadium species in different oxidation states.[19]

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.[20][21]

Niobates are generated by dissolving the pentoxide in basic hydroxide solutions or by melting it in alkali metal oxides. Examples are lithium niobate (LiNbO3) and lanthanum niobate (LaNbO4). In the lithium niobate is a trigonally distorted perovskite-like structure, whereas the lanthanum niobate contains lone NbO3−
4 ions.[6]

Tantalates, compounds containing [TaO4]3− or [TaO3]− are numerous. Lithium tantalate (LiTaO3) adopts a perovskite structure. Lanthanum tantalate (LaTaO4) contains isolated TaO3−
4 tetrahedra.[6]

Halides and their derivatives[edit]

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.[22] 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.

A very pure sample of niobium pentachloride

Niobium forms halides in the oxidation states of +5 and +4 as well as diverse substoichiometric compounds.[6][23] The pentahalides (NbX
5) feature octahedral Nb centres. Niobium pentafluoride (NbF5) is a white solid with a melting point of 79.0 °C and niobium pentachloride (NbCl5) is yellow (see image at left) with a melting point of 203.4 °C. Both are hydrolyzed to give oxides and oxyhalides, such as NbOCl3. The pentachloride is a versatile reagent used to generate the organometallic compounds, such as niobocene dichloride ((C
5H
5)
2NbCl
2).[24] The tetrahalides (NbX
4) are dark-coloured polymers with Nb-Nb bonds; for example, the black hygroscopic niobium tetrafluoride (NbF4) and brown niobium tetrachloride (NbCl4).

Anionic halide compounds of niobium are well known, owing in part to the Lewis acidity of the pentahalides. The most important is [NbF7]2−, an intermediate in the separation of Nb and Ta from the ores.[25] This heptafluoride tends to form the oxopentafluoride more readily than does the tantalum compound. Other halide complexes include octahedral [NbCl6]−:

As with other metals with low atomic numbers, a variety of reduced halide cluster ions is known, the prime example being [Nb6Cl18]4−.[26]

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.[25] The chloride TaCl
5, which exists as a dimer, is the main reagent in synthesis of new Ta compounds. It hydrolyzes readily to an oxychloride. The lower halides TaX
4 and TaX
3, feature Ta-Ta bonds.[6][23]

Physical properties[edit]

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-blue refractory metals, though impurities of carbon, nitrogen, and oxygen make them brittle.[27] They all crystallize in the body-centerd cubic structure at room temperature,[28] and dubnium is expected to do the same.[29]

The table below is a summary of the key physical properties of the group 5 elements. The four question-marked values are extrapolated.[30]

Vanadium[edit]

Vanadium is an average-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.[33][34] 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.[6] It is oxidized in air at about 933 K (660 °C, 1220 °F), although an oxide passivation layer forms even at room temperature.

Niobium[edit]

Niobium is a lustrous, grey, ductile, paramagnetic metal in group 5 of the periodic table (see table), with an electron configuration in the outermost shells atypical for group 5. Similary atypical configurations occur in the neighborhood of ruthenium (44), rhodium (45), and palladium (46).

Although it is thought to have a body-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.[35] Therefore, further research and discovery in this area is expected.

Niobium becomes a superconductor at cryogenic temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors at 9.2 K.[36] Niobium has the greatest magnetic penetration depth of any element.[36] In addition, it is one of the three elemental Type II superconductors, along with vanadium and technetium. The superconductive properties are strongly dependent on the purity of the niobium metal.[37]

When very pure, it is comparatively soft and ductile, but impurities make it harder.[38]

The metal has a low capture cross-section for thermal neutrons;[39] thus it is used in the nuclear industries where neutron transparent structures are desired.[40]

Tantalum[edit]

Tantalum is dark (blue-gray),[41] dense, ductile, very hard, easily fabricated, and highly conductive of heat and electricity. The metal is renowned for its resistance to corrosion by acids; in fact, at temperatures below 150 °C tantalum is almost completely immune to attack by the normally aggressive aqua regia. It can be dissolved with hydrofluoric acid or acidic solutions containing the fluoride ion and sulfur trioxide, as well as with a solution of potassium hydroxide. Tantalum's high melting point of 3017 °C (boiling point 5458 °C) is exceeded among the elements only by tungsten, rhenium and osmium for metals, and carbon.

Tantalum exists in two crystalline phases, alpha and beta. The alpha phase is relatively ductile and soft; it has body-centered cubic structure (space group Im3m, lattice constant a = 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 is tetragonal (space group P42/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[42] obtained by magnetron sputtering, chemical vapor deposition or electrochemical deposition from a eutectic molten salt solution.[43]

Dubnium[edit]

Relativistic (solid line) and nonrelativistic (dashed line) radial distribution of the 7s valence electrons in dubnium.

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 of electromagnetic attraction between an electron and a nucleus. Similar effects have been found for the outermost s orbitals (and p1/2 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.[30]

A more indirect effect is that the contracted s and p1/2 orbitals shield 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.[30]

Relativistic stabilization of the ns orbitals, the destabilization of the (n-1)d orbitals and their spin–orbit splitting for the group 5 elements.

Another effect is the spin–orbit interaction, particularly spin–orbit splitting, which splits the 6d subshell—the azimuthal 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, 6d3/2.)[30]

A singly 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.[30]

Atoms of dubnium in the solid state should arrange themselves in a body-centered cubic configuration, like the previous group 5 elements.[29] The predicted density of dubnium is 21.6 g/cm3.[31]

Production[edit]

Approximately 70000 tonnes of vanadium ore are produced yearly, with 25000 t of vanadium ore being produced in Russia, 24000 in South Africa, 19000 in China, and 1000 in Kazakhstan. 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 heating vanadium oxide with calcium in a pressure vessel. Very high-purity vanadium is produced from a reaction of vanadium trichloride with magnesium.[5]

230,000 t of niobium ore are produced yearly, with Brazil producing 210,000 t, Canada producing 10000 t, and Australia producing 1000 t. 60000 t of pure niobium are produced each year.[5]

70000 t of tantalum ore are produced yearly. Brazil produces 90% of tantalum ore, with Canada, Australia, China, and Rwanda also producing the element. The demand for tantalum is around 1200 t per year.[5]

Dubnium is produced synthetically by bombarding actinides with lighter elements.[5]

Occurrence[edit]

There are 160 parts per million of vanadium in the earth's crust, making it the 19th most abundant element there. Soil contains on average 100 parts per million of vanadium, and seawater contains 1.5 parts per billion of vanadium. A typical human contains 285 parts per billion of vanadium. Over 60 vanadium ores are known, including vanadinite, patronite, and carnotite.[5]

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 per quadrillion of niobium. A typical human contains 21 parts per billion of niobium. Niobium is in the minerals columbite and pyrochlore.[5]

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 minerals tantalite and pyrochlore.[5]

Applications[edit]

Vanadium's main application is in alloys, such as vanadium steel. Vanadium alloys are used in springs, tools, jet engines, armor plating, and nuclear reactors. Vanadium oxide gives ceramics a golden color, and other vanadium compounds are used as catalysts to produce polymers.[5]

Small amounts of niobium are added to stainless steel to improve its quality. Niobium alloys are also used in rocket nozzles because of niobium's high corrosion resistance.[5]

Tantalum has four main types of applications. Tantalum is added into objects exposed to high temperatures, in electronic devices, in surgical implants, and for handling corrosive substances.[5]

Biological occurrences[edit]

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 in biology, and is more important in ocean environments than on land.

Vanadium, essential to ascidians and tunicates as vanabins, has been known in the blood cells of Ascidiacea (sea squirts) since 1911,[44][45] 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).[46] Vanadium-dependent bromoperoxidase generates organobromine compounds in a number of species of marine algae.[47]

Rats and chickens are also known to require vanadium in very small amounts and deficiencies result in reduced growth and impaired reproduction.[48] Vanadium is a relatively controversial dietary supplement, primarily for increasing insulin sensitivity[49] and body-building. Vanadyl sulfate may improve glucose control in people with type 2 diabetes.[50] 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.[51]

Toxicity and precautions[edit]

Pure vanadium is not known to be toxic. However, vanadium pentoxide causes severe irritation of the eyes, nose, and throat.[5] Tetravalent VOSO4 has been reported to be at least 5 times more toxic than trivalent V2O3.[52] The Occupational Safety and Health Administration (OSHA) 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.[53] 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.[53] Vanadium compounds are poorly absorbed through the gastrointestinal system. Inhalation of vanadium and vanadium compounds results primarily in adverse effects on the respiratory system.[54][55][56] 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,[57][58] liver,[59] neurological development,[60] and other organs[61] 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,[55] although the interpretation of the results has recently been disputed.[62] The carcinogenicity of vanadium has not been determined by the United States Environmental Protection Agency.[63] 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.[64][65]

Niobium has no known biological role. While niobium dust is an eye and skin irritant[5] 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.[66][67] 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 a median lethal dose (LD50) between 10 and 100 mg/kg.[68][69][70] For oral administration the toxicity is lower; a study with rats yielded a LD50 after seven days of 940 mg/kg.[68]

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.[5] The metal is highly biocompatible[71] and is used for body implants and coatings, therefore attention may be focused on other elements or the physical nature of the chemical compound.[72] People can be exposed to tantalum in the workplace by breathing it in, skin contact, or eye contact. The Occupational 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. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) 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 is immediately dangerous to life and health.[73]

References[edit]

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Further reading[edit]

• 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.

Which element has a valency of 5?

What is Group 5 called?

Does Group 5 have 5 valence electrons?

What is the valency of group 2?