Rhenium (Re)
Element 75 · Transition metal · atomic mass 186.21 u · group 7, period 6
Electron shells: 2, 8, 18, 32, 13, 2
Rhenium was the last stable element to be discovered and is among the rarest in the crust. Jet-engine turbine blades depend on it to survive their operating temperatures.
Discovered in 1925, rhenium was the last element with stable isotopes to be found.
- Atomic number
- 75
- Atomic mass
- 186.21 u
- Electron configuration
- [Xe] 6s² 4f¹⁴ 5d⁵
- Group · period · block
- 7 · 6 · d
- Oxidation states
- +4, +6, +7
- Electronegativity
- 1.9 (Pauling)
- Melting point
- 3,186 °C
- Boiling point
- 5,596 °C
- Density
- 20.8 g/cm³
- State at 20 °C
- Solid
- Appearance
- Silvery-white metal
- Discovered
- Walter Noddack, Ida Tacke and Otto Berg, 1925
75 protons, and 75 electrons when neutral
IUPAC standard atomic weight
Manganese group
What Rhenium is used for
- Single-crystal jet turbine blades
- Petroleum reforming catalysts
- High-temperature thermocouples
- Filaments for mass spectrometers
Atomic structure of Rhenium
A neutral rhenium atom has 75 protons and 75 electrons. Its most common isotope carries about 111 neutrons, which is where the mass number 186 comes from. Change the neutron count and you have a different isotope of rhenium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 32, 13, 2. In orbital notation that is [Xe] 6s² 4f¹⁴ 5d⁵. As a d-block element its valence count is variable, which is why it can form compounds in several oxidation states.
3D electron orbitals
See where Rhenium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Rhenium sits in the periodic table
The d-block. Multiple stable oxidation states give them coloured compounds, catalytic ability and the strength that makes them the working metals of industry.
- Directly above: Technetium — same group, so similar chemistry with a smaller atom.
- Directly below: Bohrium — same group, one shell larger.
- One proton lighter: Tungsten.
- One proton heavier: Osmium.
Discovery and naming
Rhenium was discovered by Walter Noddack, Ida Tacke and Otto Berg in 1925. Its name comes from Latin Rhenus, "the Rhine", which is also why its symbol (Re) does not match its English name.
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Rhenium?
The standard atomic weight of Rhenium is 186.21 u, as published by IUPAC's Commission on Isotopic Abundances and Atomic Weights.
How many protons, neutrons and electrons does Rhenium have?
Rhenium has 75 protons, because the atomic number is the proton count and that is what makes an atom Rhenium at all. A neutral Rhenium atom has the same number of electrons, 75. The neutron count varies by isotope; the most common one has about 111, since 186 − 75 = 111.
What is the electron configuration of Rhenium?
The electron configuration of Rhenium is [Xe] 6s² 4f¹⁴ 5d⁵. Its electrons are arranged 2, 8, 18, 32, 13, 2 across 6 shells.
Is Rhenium a metal?
Yes. Rhenium is classified as a transition metal, on the metallic side of the table.
What group and period is Rhenium in?
Rhenium is in group 7 (the manganese group), period 6, in the d-block. The group is its column and the period is its row.
What is the charge of Rhenium?
Rhenium most commonly forms a 7+ or 4+ ion. Like most transition metals it has several accessible oxidation states, so the charge depends on the compound. Across all its compounds it shows oxidation states of +4, +6, +7.
What is the melting point of Rhenium?
Rhenium melts at 3,186 °C and boils at 5,596 °C. That puts it in the solids at everyday temperatures.
What is Rhenium used for?
Single-crystal jet turbine blades, Petroleum reforming catalysts, High-temperature thermocouples, Filaments for mass spectrometers. Rhenium was the last stable element to be discovered and is among the rarest in the crust.
Who discovered Rhenium, and where does its name come from?
Rhenium (Re) was discovered by Walter Noddack, Ida Tacke and Otto Berg in 1925. The name comes from Latin Rhenus, "the Rhine".