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Rhenium

Chemical element, symbol Re and atomic number 75 / From Wikipedia, the free encyclopedia

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Rhenium is a chemical element; it has symbol Re and atomic number 75. It is a silvery-gray, heavy, third-row transition metal in group 7 of the periodic table. With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust. It has the third-highest melting point and second-highest boiling point of any element at 5869 K.[6] It resembles manganese and technetium chemically and is mainly obtained as a by-product of the extraction and refinement of molybdenum and copper ores. It shows in its compounds a wide variety of oxidation states ranging from −1 to +7.

Quick facts: Rhenium, Pronunciation, Appearance, Standard ...
Rhenium, 75Re
Rhenium_single_crystal_bar_and_1cm3_cube.jpg
Rhenium
Pronunciation/ˈrniəm/ (REE-nee-əm)
Appearancesilvery-grayish
Standard atomic weight Ar°(Re)
Rhenium in the periodic table
Tc

Re

Bh
tungstenrheniumosmium
Atomic number (Z)75
Groupgroup 7
Periodperiod 6
Block  d-block
Electron configuration[Xe] 4f14 5d5 6s2
Electrons per shell2, 8, 18, 32, 13, 2
Physical properties
Phase at STPsolid
Melting point3459 K (3186 °C, 5767 °F)
Boiling point5903 K (5630 °C, 10,170 °F)
Density (near r.t.)21.02 g/cm3
when liquid (at m.p.)18.9 g/cm3
Heat of fusion60.43 kJ/mol
Heat of vaporization704 kJ/mol
Molar heat capacity25.48 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 3303 3614 4009 4500 5127 5954
Atomic properties
Oxidation states−3, −1, 0, +1, +2, +3, +4, +5, +6, +7 (a mildly acidic oxide)
ElectronegativityPauling scale: 1.9
Ionization energies
  • 1st: 760 kJ/mol
  • 2nd: 1260 kJ/mol
  • 3rd: 2510 kJ/mol
  • (more)
Atomic radiusempirical: 137 pm
Covalent radius151±7 pm
Color lines in a spectral range
Spectral lines of rhenium
Other properties
Natural occurrenceprimordial
Crystal structure hexagonal close-packed (hcp)
Hexagonal close packed crystal structure for rhenium
Speed of sound thin rod4700 m/s (at 20 °C)
Thermal expansion6.2 µm/(m⋅K)
Thermal conductivity48.0 W/(m⋅K)
Electrical resistivity193 nΩ⋅m (at 20 °C)
Magnetic orderingparamagnetic[3]
Molar magnetic susceptibility+67.6×10−6 cm3/mol (293 K)[4]
Young's modulus463 GPa
Shear modulus178 GPa
Bulk modulus370 GPa
Poisson ratio0.30
Mohs hardness7.0
Vickers hardness1350–7850 MPa
Brinell hardness1320–2500 MPa
CAS Number7440-15-5
History
Namingafter the river Rhine (German: Rhein)
DiscoveryMasataka Ogawa (1908)
First isolationMasataka Ogawa (1919)
Named byWalter Noddack, Ida Noddack, Otto Berg (1925)
Isotopes of rhenium
Main isotopes[5] Decay
abun­dance half-life (t1/2) mode pro­duct
185Re 37.4% stable
186Re synth 3.7185 d β 186Os
ε 186W
186mRe synth 2×105 y IT 186Re
β 186Os
187Re 62.6% 4.12×1010 y β 187Os
Symbol_category_class.svg Category: Rhenium
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Rhenium was originally discovered by Masataka Ogawa in 1908, but he mistakenly assigned it as element 43 rather than element 75 and named it nipponium. It was rediscovered by Walter Noddack, Ida Tacke and Otto Berg in 1925,[7] who gave it its present name. It was named after the river Rhine in Europe, from which the earliest samples had been obtained and worked commercially.[8]

Nickel-based superalloys of rhenium are used in combustion chambers, turbine blades, and exhaust nozzles of jet engines. These alloys contain up to 6% rhenium, making jet engine construction the largest single use for the element. The second-most important use is as a catalyst: it is an excellent catalyst for hydrogenation and isomerization, and is used for example in catalytic reforming of naphtha for use in gasoline (rheniforming process). Because of the low availability relative to demand, it is expensive, with price reaching an all-time high in 2008/2009 of US$10,600 per kilogram (US$4,800 per pound). Due to increases in recycling and a drop in demand for rhenium in catalysts, the price had dropped to US$2,844 per kilogram (US$1,290 per pound) as of July 2018.[9]

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