Chemical element · reference page

75Re

Rhenium

Rhenium is element 75 (Re), located in period 6, group 7 and the d block. At room temperature its reference phase is solid. Its electron configuration is [Xe] 4f14 5d5 6s2.

Atomic number75

Standard atomic weight186.207(1)

Group7

Period6

Blockd

Electron configuration[Xe] 4f14 5d5 6s2

Electronic structure

What controls its chemistry

The d subshell participates in the chemistry of rhenium. Transition metals can use electrons of similar energies in bonding, which is why variable oxidation states, coordination compounds and catalytic behaviour are common across the d block.

Its electron configuration, [Xe] 4f14 5d5 6s2, should be read together with the oxidation state of the compound: removing electrons changes which d orbitals are occupied and can alter colour, magnetism, bonding and reactivity.

Chemical forms

Compounds, ions and materials

For rhenium, important chemical forms include metals and alloys, oxides, halides and coordination compounds. Variable oxidation states are common because s and d electrons have similar energies, and ligands around the metal ion can strongly alter colour, magnetism and reactivity.

Physical behaviour

State and phase changes

The reference phase at room temperature is solid. The listed density is 21.02 g/cm³. The melting point is 3 463 K (3 190 °C). The boiling point is 5 869 K (5 596 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where rhenium is found and used

In practice, rhenium is encountered in jet engines, catalysts and thermocouples.

In practice

Examples of real uses

Jet engines

Rhenium is used in high-temperature superalloys that retain strength in turbine components.

Catalysts

Rhenium is used to accelerate chemical reactions without being consumed in the overall reaction.

Thermocouples

Rhenium is used in temperature-sensing alloys whose voltage changes predictably with temperature.

Periodic position

What its neighbours tell us

Rhenium is in period 6 and group 7. In the neighbourhood shown here, it lies between tungsten and osmium in the same period; technetium is above it and bohrium below it in the same group. These positions make it possible to compare atomic size, ionisation energy and bonding behaviour with nearby elements.

Reference data

Physical and atomic properties

Classificationtransition metal

Phase at room temperatureSolid

Electron shells2 · 8 · 18 · 32 · 13 · 2

Density21.02 g/cm³

Melting point3 463 K (3 190 °C)

Boiling point5 869 K (5 596 °C)

Pauling electronegativity1.9

First ionisation energy756kJ/mol

Electron affinity5.8273 kJ/mol

Values describe the element or neutral atom where applicable. Physical data can depend on allotrope, pressure and measurement conditions.

History

Discovery and identification

The discovery of rhenium is associated with Masataka Ogawa. Recognition of the element, isolation of a pure sample and assignment of its modern atomic number did not necessarily occur at the same time.

Isotopes and atomic weight

How isotope composition changes the numbers

The standard atomic weight is 186.207(1). This value refers to the isotopic composition of natural terrestrial material, not to the mass of one specific atom.

Rhenium has at least one stable isotope. Different isotopes have the same number of protons and therefore the same element identity, but different neutron numbers and atomic masses.

Safety

Handling and exposure

The hazards associated with rhenium depend on chemical form, dose and route of exposure. Pure rhenium, its ions and its compounds can have very different biological and environmental effects, so safety data should be checked for the actual substance being handled.