Rhenium (Re)
Stable isotopes of rhenium available from ISOFLEX
| Isotope | Z(p) | N(n) | Atomic Mass | Natural Abundance | Enrichment Level | Chemical Form |
| Re-185 | 75 | 110 | 184.952955 | 37.40% | 93.00-96.80% | Metal |
| Re-187 | 75 | 112 | 186.955750 | 62.60% | >99.00% | Metal |
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Rhenium was discovered in 1925 by Walter Noddack, Ida Tacke and Otto Berg. Its name derives from the Greek name Rhenus, meaning “River Rhine.”
A silver-white solid or gray-to-black powder, rhenium has a hexagonal crystal system, which it retains all the way to its melting point. It has the widest range of valences of any element. It is insoluble in water, practically insoluble in hydrochloric acid, soluble in dilute nitric acid and hydrogen peroxide, and slightly soluble in sulfuric acid. It is not attacked by sea water, hydrochloric acid, cold sulfuric or hydrofluoric acids. It is attacked by strong oxidizing agents (nitric and sulfuric acids). In compact or massive form, it is stable at ordinary temperatures. Rhenium reacts with all halogens, including iodine, to yield halides in several valence states. However, oxidizing acids — such as nitric acid or hot sulfuric acid — vigorously react with the metal, forming perrhenic acid. Rhenium combines with phosphorus, arsenic, silicon, selenium and tellurium at elevated temperatures, forming binary compounds. The metal, however, is stable in hydrogen and nitrogen at high temperatures.
Rhenium is used in tungsten- and molybdenum-based alloys. It is used for filaments for ion gauges in mass spectrometers. Rhenium-tungsten alloys are used in thermocouples to measure temperatures up to 2200 ºC. Rhenium wire is used in flash bulbs for photography. Rhenium compounds also are used as catalysts in hydrogenation and hydrofracking reactions in petroleum refining.
Properties of Rhenium
| Name | Rhenium |
| Symbol | Re |
| Atomic number | 75 |
| Atomic weight | 186.21 |
| Standard state | Solid at 298 ºK |
| CAS Registry ID | 7440-15-5 |
| Group in periodic table | 7 |
| Group name | None |
| Period in periodic table | 6 |
| Block in periodic table | d-block |
| Color | Grayish white |
| Classification | Metallic |
| Melting point | 3180 °C |
| Boiling point | 5627 °C |
| Vaporization point | 5627 ºC |
| Thermal conductivity | 48.0 W/(m·K) at 298.2 °K |
| Electrical resistivity | 19.14 µΩ·cm at 20 °C |
| Electronegativity | 1.9 |
| Specific heat | 0.14 kJ/kg K |
| Heat of vaporization | 705 kJ·mol-1 |
| Heat of fusion | 33 kJ·mol-1 |
| Density of liquid | 18.9 g/cm3 at 3180 °C |
| Density of solid | 20.53 g/cm3 |
| Electron configuration | [Xe]4f145d56s2 |
| Oxidation states | -1, +1, +2, +3, +4, +5, +6, +7 |
| Most common oxidation state | +7 |
