History and Production
From Latin Rhenus, meaning Rhine. It was discovered in 1925 by W. Noddack, I. Tacke and O. Berg in a sample of gadolinite, molybdenite and platinum ores. They were able to extract only 1 g of the metal out of 660 kg of molybdenite. It was also independently discovered by F.H. Loring and J.F.G. Druce in manganese compounds.
In fact it was the last naturally occuring element to be discovered. It is now recovered from the flue dust produced in the roasting of molybdenum sulfide ores. It is used in spectrometer filaments, furnace heater windings, thermocouples (Re-W up to 2200°C) and electrical contacts. It is also used as a catalyst in hydrogenation and dehydrogenation
processes such as petroleum refining.
The metal is lustrous and silvery white. It is the second highest melting point (after tungsten) metal. It is widely spread but very rare in earth, about 0.0007 ppm and does not occur free in nature, nor as any specific mineral.
It is usually associated with molybdenite ores (up to 0.2%).
Interatomic distance: 274.2 pm
Melting point: 3186°C
Boiling point: 5596°C
Thermal conductivity/Wm-1K-1: 47.9 (27°C)
Density/kgm-3: 21020 (20°C), 18900 (m.p.)
Standard Thermodynamic Data (atomic gas)
Enthalpy of formation: 769.9 kJ/mol
Gibbs free energy of formation: 724.6 kJ/mol
Entropy: 188.9 J/mol K
Heat capacity: 20.8 J/mol K
Electronic configuration: [Xe] 4f14 5d5 6s2
Term symbol: 6S5/2
Electron affinity: 14.4728 kJ/mol Electronegativity (Pauline): 1.70
Ionization energy (first, second, third): 755.818, -, - kJ/mol