Rhenium, Physical and Chemical Properties

Physical Properties

Rhenium is a transition metal. Like the other members of the group it is less reactive than the typical metals but more reactive than the less typical metals. The transition metals are characterized by having the outermost electron shell containing two electrons and the next inner shell an increasing number of electrons. Because of the small energy differences between the valence shells, a number of oxidation states occur. The metal occurs in nature in association with molybdenite, MoS₂, which in turn is associated with chalocopyrite in porphyry copper ores. Molybdenite occurring in quartz veins does not contain rhenium.

Atomic number	75
Atomic weight	186.207
Relative abundance in the Earth’s crust, %	7 × 10–8
Density at 20°C, g/cm3	21.0
Metallic radius, pm	137
Ionic radius (VII), pm	53
Melting point, °C	3,180
Boiling point, °C	5,870
Heat of fusion, kJ/mol	33
Heat of sublimation  ΔH B (monatomic gas)	+ 779 (± 8) kJ/mol
Enthalpy of formation of Re2O7, kJ/mol	–1,241
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