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