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Rhenium,  75Re
General properties
Name, symbol Rhenium, Re
Appearance Silvery-gray metal
Rhenium in the periodic table


Atomic number 75
Standard atomic weight (Ar) 186.207(1)
Group, block VII; d-block
Period period 6
Electron configuration [Xe] 4f14 5d5 6s2
per shell
2, 8, 18, 32, 13, 2
Physical properties
Phase Solid
Melting point 3459 K ​(3186 °C, ​​5767 °F)
Boiling point 5869 K ​(5596 °C, ​10,105 °F)
Density near r.t. 21.02 g/cm3
when liquid, at  18.9 g/cm3
Heat of fusion 60.43 kJ/mol
Heat of 704 kJ/mol
Molar heat capacity 25.48 J/(mol·K)
Atomic properties
Oxidation states 7, 6, 5, 4, 3, 2, 1, 0, −1, −3 ​​(a mildly acidic oxide)
Electronegativity Pauling scale: 1.9
energies 1st: 760 kJ/mol
2nd: 1260 kJ/mol
3rd: 2510 kJ/mol
Atomic radius empirical: 137 pm
Covalent radius 151±7 pm
Crystal structure ​hexagonal close-packed (hcp)
Speed of sound thin rod 4700 m/s (at 20 °C)
Thermal expansion 6.2 µm/(m·K)
Thermal conductivity 48.0 W/(m·K)
Electrical resistivity 193 Ω·m (at 20 °C)
Magnetic ordering Paramagnetic
Young's modulus 463 GPa
Shear modulus 178 GPa
Bulk modulus 370 GPa
Poisson ratio 0.30
Mohs hardness 7.0
Vickers hardness 1350–7850 MPa
Brinell hardness 1320–2500 MPa
CAS Registry Number 7440-15-5
Naming after the river Rhine (German: Rhein)
Discovery and first isolation Masataka Ogawa (1908)
Named by Walter Noddack, Ida Noddack, Otto Berg (1922)
· references

Rhenium is a chemical element with symbol Re and atomic number 75. It is a silvery-gray or silvery-white, 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.



Rhenium resembles manganese and technetium chemically. Rhenium has good chemical resistance to acids, such as sulfuric acid, hydrochloric acid, aqua regia, as well as alkalis, but it dissolves in concentrated nitric acid. It also reacts with halogens at high temperatures, such as fluorine at 400 °C.


Rhenium is a silvery-white (or gray) hard metal. Rhenium has with one of the highest melting points of all elements (3186 °C), third after tungsten and carbon (though carbon is not a metal and does not melt under standard pressure). It also has the highest boiling point of all elements (5596 °C). Rhenium's density (21.02 g/cm3) is only exceeded by platinum, iridium and osmium. These properties make rhenium a valuable metal in the manufacturing of superalloys.


Rhenium is sold by various chemical suppliers and other metal companies, though it's not cheap.


Rhenium can be obtained by reducing ammonium perrhenate at high temperatures with a reducing agent, such as hydrogen.

2 NH4ReO4 + 7 H2 → 2 Re + 8 H2O + 2 NH3

Heating must be done slowly because ammonium perrhenate decomposes to volatile Re2O7 starting at 250 °C. When heated in a sealed tube at 500 °C, APR decomposes to rhenium dioxide:

2NH4ReO4 → 2ReO2 + N2 + 4 H2O

Melting the powder can only be done using an electric arc furnace, in an inert atmosphere.


  • Make ammonium perrhenate
  • Metal coatings
  • Catalysts
  • Make rhenium(VII) oxide



Little is known about rhenium's biological effects. Medical studies performed on animals indicate that both the metal and its salts show little toxicity, though only potassium perrhenate and rhenium trichloride have been tested.


Rhenium can be stored in any container, though it should be kept away from nitric acid.


Due to its rarity, it's best to recycle rhenium and its compounds as much as possible, instead of throwing it away.


Relevant Sciencemadness threads