|Name, symbol||Rhenium, Re|
|Rhenium in the periodic table|
|Standard atomic weight (Ar)||186.207(1)|
|Group, block||VII; d-block|
|Electron configuration||[Xe] 4f14 5d5 6s2|
|2, 8, 18, 32, 13, 2|
|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)|
|Oxidation states||7, 6, 5, 4, 3, 2, 1, 0, −1, −3 (a mildly acidic oxide)|
|Electronegativity||Pauling scale: 1.9|
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)|
|Young's modulus||463 GPa|
|Shear modulus||178 GPa|
|Bulk modulus||370 GPa|
|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)|
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 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.
- 2 NH4ReO4 + 7 H2 → 2 Re + 8 H2O + 2 NH3
The rhenium obtained this way is in powdered form.
- 2 NH4ReO4 → 2 ReO2 + N2 + 4 H2O
Melting the powder to bulk metal can only be done using an electric arc furnace, in an inert atmosphere.
- Make ammonium perrhenate
- Metal coatings
- 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.