Rhenium
[Xe] 4f¹⁴ 5d⁵ 6s² · 2 · 8 · 18 · 32 · 13 · 2
The last stable element discovered in nature and one of the rarest. Rhenium holds the second-highest melting point after tungsten and is indispensable in the turbine blades of jet engines.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 75
- Atomic mass
- 186.207 а.е.м.
- Electron configuration
- [Xe] 4f¹⁴ 5d⁵ 6s²
- Electrons per shell
- 2 · 8 · 18 · 32 · 13 · 2
- Block
- d-block
- Group
- Manganese group
- Period
- 6
- Electronegativity (Pauling)
- 1.9
- Electronegativity (Allen)
- 1.6
- Atomic radius
- 188 pm
- Covalent radius
- 151 pm
- Van der Waals radius
- 217 pm
- Ionisation energy 1
- 760 kJ/mol
- Ionisation energy 2
- 1 260 kJ/mol
- Ionisation energy 3
- 2 510 kJ/mol
- Ionisation energy 4
- 3 640 kJ/mol
- Electron affinity
- 14.5 kJ/mol
- Common oxidation states
- +4, +7
- Oxidation states
- -3, -1, +1, +2, +3, +4, +5, +6, +7
Physical properties
- State at 25 °C
- solid
- Density
- 21.02 g/cm³
- Melting point
- 3 459 K · 3 185.9 °C
- Boiling point
- 5 869 K · 5 595.9 °C
- Speed of sound
- 4 700 m/s
Thermal properties
- Heat of fusion
- 60.43 kJ/mol
- Heat of vaporisation
- 704 kJ/mol
- Specific heat capacity
- 0.137 J/(g·K)
- Thermal conductivity
- 48 W/(m·K)
Mechanical properties
- Young's modulus
- 463 GPa
- Shear modulus
- 178 GPa
- Bulk modulus
- 370 GPa
- Poisson ratio
- 0.3
- Mohs hardness
- 7
- Brinell hardness
- 1 320 MPa
Electrical and magnetic properties
- Electrical resistivity
- 193 nΩ·m
- Magnetic ordering
- paramagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- 1.7 K
Crystal structure
- Crystal structure
- hexagonal close-packed (hcp)
- Lattice constants
- a = 276.1 pm · c = 445.6 pm
Abundance
- In the crust
- 0.0007 mg/kg
- In the ocean
- 8.4·10⁻⁶ mg/L
- In the universe
- 0.002 mg/kg
- In the human body
- no data
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 185Re | 37.4 % | stable | — |
| 187Re | 62.6 % | 41.2 Gyr | β− |
Rhenium-187 is radioactive with a 41-billion-year half-life; rhenium-osmium dating is applied to sulfide ores and meteorites.
Discovery
- Year of discovery
- 1925
- Discovered by
- Walter Noddack, Ida Tacke and Otto Berg
- Where
- Germany
- Origin of the name
- from Rhenus, the Latin name for the Rhine
History
Mendeleev predicted box 75, but the element was not found until 1925, when Walter Noddack, Ida Tacke and Otto Berg in Germany extracted one gram from 660 kilograms of molybdenite. It is named after the Rhine.
Where it occurs
0.0007 mg/kg of the crust — one of the rarest non-radioactive elements. It has almost no minerals of its own and follows molybdenum.
How it is produced
Captured from the flue gas of roasting molybdenum concentrates. World output is about 50 tonnes a year.
Role in living things
No biological role.
Safety
Of low toxicity. The oxide Re₂O₇ is volatile and irritates the airways.
Uses
- Nickel superalloys for turbine blades: rhenium raises an engine's operating temperature by tens of degrees
- Platinum-rhenium catalysts for petrol reforming
- Thermocouples and mass spectrometer filaments
- Electrical contacts that have to survive arcing
Curiosities
- Rhenium was the last stable element found in natural material; everything discovered later was synthesised.
- About 80 % of the world's rhenium goes into aircraft engines.
- Ida Tacke was the first to suggest that uranium nuclei might split — four years before Hahn and Strassmann, and her paper was ignored.
- Rhenium has the highest boiling point of any element, 5869 K.