Rhenium
transition metalProperties
| Property | Value |
|---|---|
| Atomic Mass | 186.21 amu |
| Category | transition metal |
| Group | 7 |
| Period | 6 |
| Electron Configuration | [Xe] 4f14 5d5 6s2 |
| Electronegativity | 1.9 (Pauling) |
| Oxidation States | 7, 6, 4, 2, -1 |
| Melting Point | 3459 K (3185.8 °C) |
| Boiling Point | 5869 K (5595.9 °C) |
| Density | 21.02 g/cm³ |
| Discovered By | Masataka Ogawa, Walter Noddack, Ida Noddack, Otto Berg (1925) |
About Rhenium
Rhenium was the last stable element pulled out of nature, hiding in molybdenite at parts-per-billion concentrations until the Noddacks and Berg X-ray-fluoresced it out of platinum residues in 1925. The numbers are extreme even for a refractory metal: melting point 3186 °C (third behind tungsten and carbon), boiling point 5596 °C (highest of any element), and a crustal abundance around 0.7 ppb that makes it scarcer than gold. The chemistry spans nine oxidation states from −1 to +7, with the perrhenate ion ReO₄⁻ as the stable end and Re(I) carbonyl and Re(III) chloride clusters as workhorses for organometallic synthesis. Single-crystal nickel superalloys with 3–6% rhenium hold their creep strength at 1100 °C in the hottest stage of jet turbines, which is why nearly 70% of the world's roughly 60 tonnes/year output goes into engine blades. The other big sink is bimetallic Pt-Re/Al₂O₃ catalytic-reforming catalysts that convert naphtha into high-octane gasoline.
Fun Fact
Rhenium was the last stable element found in nature — it took until 1925 because rhenium is so dispersed in the Earth's crust that no concentrated ore deposits exist, and it is mostly recovered as a byproduct of molybdenum mining.
Common Uses
- Single-crystal nickel superalloys (CMSX-4, René N6) for HP turbine blades at 1100 °C
- Pt-Re/Al₂O₃ catalysts for catalytic reforming of naphtha to high-octane reformate
- W-Re thermocouples (types C and D) for measurements above 2000 °C in vacuum
- Filaments and ion-source ribbons in mass spectrometers for Os-Re geochronology
- Hydrogenation catalysts for ammonia synthesis and selective olefin chemistry
- Re-188 generator-produced beta emitter for palliative bone-pain radiotherapy