Rhenium
Atomic Data
| Atomic Number | 75 |
| Symbol | Re |
| Atomic Weight | 186.21 u |
| Density (STP) | 21.02 g/cm³ |
| Melting Point | 3185.85 °C (3459 K) |
| Boiling Point | 5595.85 °C (5869 K) |
| Electronegativity | 1.9 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d5 6s2 |
| Oxidation States | +4, +7 |
| Phase at STP | Solid |
| Category | Transition Metal |
| Period / Group | 6 / 7 |
| CAS Number | 7440-15-5 |
Electron Configuration
[Xe] 4f14 5d5 6s2
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 10 | 28 |
| N | 4 | 4s | 2 | 30 |
| N | 4 | 4p | 6 | 36 |
| N | 4 | 4d | 10 | 46 |
| N | 4 | 4f | 14 | 60 |
| O | 5 | 5s | 2 | 62 |
| O | 5 | 5p | 6 | 68 |
| O | 5 | 5d | 5 | 73 |
| P | 6 | 6s | 2 | 75 |
| Total | 75 | 75 | ||
Isotopes of Rhenium
Rhenium has two naturally occurring stable isotopes. The most abundant is ¹⁸⁷Re, comprising 62.6% of all naturally occurring Rhenium.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Rhenium-185 | ¹⁸⁵Re | 75 | 110 | 37.4 | Stable |
| Rhenium-187 | ¹⁸⁷Re | 75 | 112 | 62.6 | Stable |
Abundance & Occurrence
Rhenium is present in Earth's crust at approximately 0.0007 ppm by mass and at approximately 0.2 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Rhenium heptoxide dust: Re2O7 and other rhenium oxide dusts are mildly corrosive and irritating to the respiratory tract, skin, and eyes; use ventilation and PPE when handling powders.
- Perrhenic acid: Concentrated perrhenic acid (HReO4) is corrosive; contact with skin and eyes requires immediate washing.
- Fire hazard: powder: Rhenium metal powder is combustible at elevated temperatures; standard metal powder safety precautions apply.
- General toxicity: Rhenium has low acute systemic toxicity in available data; it is used in very small quantities industrially and does not present a widespread occupational hazard.
Rhenium in the Real World
Real-World Uses
- Superalloy turbine blades: Rhenium (3–6%) added to single-crystal nickel superalloys dramatically improves creep resistance at temperatures above 1000 °C, enabling higher turbine inlet temperatures and greater fuel efficiency in jet engines and gas turbines.
- Platinum-rhenium reforming catalysts: Pt-Re/Al₂O₃ bimetallic catalysts are the workhorses of catalytic naphtha reforming in petroleum refining, producing the high-octane aromatic compounds needed for unleaded gasoline; rhenium suppresses coke formation and extends catalyst life.
- High-temperature thermocouples: Tungsten-rhenium thermocouples measure temperatures up to 2760 °C in metallurgical furnaces, plasma reactors, and hypersonic test facilities where platinum-group thermocouples fail.
- Mass spectrometer filaments: Rhenium filaments serve as the electron-emitting element in thermal ionisation mass spectrometry (TIMS) instruments used for precise isotope ratio measurements in geochronology, cosmochemistry, and nuclear safeguards verification.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is rhenium used for?
Rhenium's primary use is in nickel-based superalloy single-crystal turbine blades for jet engines. Adding 3–6% rhenium dramatically improves the blade's creep resistance at the extreme temperatures inside a jet engine. Rhenium-platinum catalysts are used in petroleum refining (catalytic reforming) to produce high-octane unleaded petrol. Rhenium-molybdenum alloys are used in thermocouples for measuring very high temperatures.
Is rhenium rare?
Yes, rhenium is one of the rarest elements in Earth's crust, with an abundance of only about 0.7 parts per billion: among the least abundant non-radioactive elements. Almost all rhenium is recovered as a byproduct of molybdenite (MoS2) roasting during copper and molybdenum production. Chile produces the largest share. Its rarity and irreplaceability in jet engine alloys make it a critical strategic material.
How was rhenium discovered?
Rhenium was the last stable element to be discovered. It was found in 1925 by German chemists Walter Noddack, Ida Tacke (Noddack), and Otto Berg, who detected it spectroscopically in gadolinite, molybdenite, and other minerals. They named it rhenium after the Rhine River. They also claimed to have discovered element 43 (masurium), but that discovery was not confirmed: element 43 later became technetium.
How does rhenium improve jet engine turbine blades?
Jet engine turbine blades operate in gases hotter than the blades' nominal melting point, relying on internal cooling channels to survive. The critical failure mode is creep: slow plastic deformation under sustained high stress at high temperature. Rhenium additions to nickel superalloys inhibit dislocation movement in the crystal lattice at high temperatures, reducing creep rates by an order of magnitude. This allows engines to run hotter and more efficiently, improving fuel economy and thrust.