Rhenium (Re)

Rhenium (symbol Re) is the chemical element with atomic number 75: a transition metal, solid at 0 °C, with an atomic mass of 186.21 u. Discovered in 1925 (Walter Noddack, Ida Tacke and Otto Berg).

Rhenium is one of the rarest elements in Earth's crust. It melts above 3,180 °C and strengthens the superalloys in the turbine blades of jet engines. In 1925 it became the last element with a stable isotope to be discovered.

Key facts

Atomic number: 75
Symbol: Re
French name: Rhénium
Atomic mass: 186.21 u
Molar mass: 186.21 g/mol
Family: Transition metals
Position: period 6, group 7, d-block
State at 0 °C: Solid
Melting point: 3,185.9 °C
Boiling point: 5,595.9 °C
Density: 21.02 g/cm³
Electronegativity (Pauling): 1.9
First ionization energy: 756 kJ/mol
Atomic radius: 135 pm
Electron configuration: [Xe] 4f¹⁴ 5d⁵ 6s²
Abundance in Earth's crust: 0.0007 ppm (81st most abundant element)
Indicative price: 3,600 $/kg (order of magnitude)
Radioactive: no
Discovery: 1925, Walter Noddack, Ida Tacke and Otto Berg

Origin of the name

From the Latin Rhenus, the Rhine.

What does rhenium look like?

A very dense (21 g/cm³), hard, silvery-white metal.

Where is rhenium found?

About 1 part per billion of Earth's crust. It has virtually no ore of its own: it travels with molybdenum in the molybdenite of copper deposits.

Natural sources

Molybdenite
Rheniite

How is rhenium produced?

Recovered from the flue gases of roasting molybdenite, itself a by-product of copper mines. It is precipitated as ammonium perrhenate, then reduced with hydrogen. World production barely exceeds 60 tonnes a year.

Top producers

Chile
United States
Poland
China

What is rhenium used for?

Single-crystal superalloys for aircraft turbine blades.
Platinum-rhenium catalysts for making high-octane gasoline.
Thermocouples for measuring very high temperatures.
Mass spectrometer filaments.

In everyday life

The engine of the plane taking you on vacation
High-octane unleaded gasoline

Role in living things

No known biological role.

Hazards of rhenium

Few data; considered mildly toxic.

Cosmic origin

Neutron stars: Created when two neutron stars collide — the “forge” of gold.

History of rhenium

In 1925 the Germans Walter Noddack, Ida Tacke and Otto Berg detected it by X-ray spectroscopy and named it after the Rhine. In 1928 they had to process about 660 kg of molybdenite to isolate a single gram of rhenium.

Did you know?

The only known rhenium-rich mineral, rheniite, was discovered in 1994 on Kudriavy volcano in the Kuril Islands.
As early as 1934, Ida Noddack suggested that uranium could break into pieces: the idea of fission, ignored at the time.
About 80% of the rhenium produced ends up in jet engines.

Isotopes of rhenium

Rhenium is a rare case: its main isotope, rhenium-187, is radioactive, and only rhenium-185 is stable. The slow transformation of rhenium-187 into osmium is used to date rocks and meteorites.

rhenium-185: 37.4% of natural rhenium, stable
rhenium-186: radioactive, half-life 3.72 days. Used to treat bone pain and arthritis.
rhenium-187: 62.6% of natural rhenium, radioactive, half-life 4.12 × 10¹⁰ years. Rhenium–osmium dating of ore deposits and meteorites.
rhenium-188: radioactive, half-life 17 h. Internal radiotherapy for tumors and skin cancers.

Related elements

Same family (transition metals): Scandium (Sc), Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn), Iron (Fe), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Yttrium (Y), Zirconium (Zr), Niobium (Nb), Molybdenum (Mo), Technetium (Tc), Ruthenium (Ru), Rhodium (Rh), Palladium (Pd), Silver (Ag), Cadmium (Cd), Hafnium (Hf), Tantalum (Ta), Tungsten (W), Osmium (Os), Iridium (Ir), Platinum (Pt), Gold (Au), Mercury (Hg), Rutherfordium (Rf), Dubnium (Db), Seaborgium (Sg), Bohrium (Bh), Hassium (Hs).

Same column (group 7): Manganese (Mn), Technetium (Tc), Bohrium (Bh).