75 Re Rhenium 186.207
Transition metal d-block Period 6 Group 7

Rhenium

Re · Element 75 · Transition metal

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One of the rarest elements in the crust, and the metal that lets jet turbines run hotter.

State at 20°C Solid
Atomic mass 186.207 u
Electron configuration[Xe] 4f¹⁴ 5d⁵ 6s²
74W All 118 76Os

Structure

The rhenium atom

Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.

Orbital cloud

Measured values

Property sheet

Every bar shows where rhenium sits among all 118 elements for that property.

Physical

Density 21.02 g/cm³ 90%
Melting point 3459 K 98%
Boiling point 5869 K 100%
Specific heat 0.137 J/g·K
Thermal conductivity 48 W/m·K 64%

Atomic

Atomic radius 137 pm 28%
Covalent radius 151 pm
Van der Waals radius 217 pm

Electronic

Electronegativity 1.9 61%
Ionisation energy 755.5 kJ/mol 62%
Electron affinity 5.8 kJ/mol 7%

Occurrence

Abundance in crust 7.00e-4 mg/kg 31%

Identity

SymbolRe
Atomic number75
Atomic mass186.207 u
CategoryTransition metal
Blockd
Crystal structurehexagonal close-packed
Oxidation states-3, -1, 0, +1, +2, +3, +4, +5, +6, +7
Discovered1925
Discovered byNoddack, Tacke & Berg

Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.

Same element, different neutrons

Isotopes of rhenium

All rhenium atoms have the same number of protons, 75, and differ only in their number of neutrons: those variants are its isotopes. The most common, Re-187, has 112 neutrons and makes up 62.60% of natural rhenium.

Isotopes of rhenium found in nature, with their share of the natural element
ISOTOPE Neutrons Natural Abundance Half-life Decay Mode
Re-185 110 37.40% Stable —
Re-187 most common 112 62.60% 4.33 × 10¹⁰ yrs β⁻

The classroom shortcut, rounded atomic mass minus atomic number, gives 111 for rhenium, but the most common rhenium atom has 112 neutrons: the atomic mass, 186.207, is an average over all natural isotopes.

Decay modes

β⁻
beta-minus decay

Data: IAEA Nuclear Data Section, LiveChart of Nuclides, ground-state evaluations, retrieved October 10, 2026. Abundance is the share of atoms in the natural element; a dash means the isotope has no standard natural abundance.

Size, to scale

How big is a rhenium atom?

Radius 137 pm — that is 0.137 nm, so about 3.65 million of them side by side would span a millimetre.

Thermal range

Solid, liquid, gas — and when

Rhenium is liquid over a 2410 K window, from 3459 K to 5869 K.

Where it sits

Position in the table

Rhenium sits in period 6, group 7. Everything in group 7 shares the same outer-electron count, which is why they behave so similarly.

Other transition metals

21Sc 22Ti 23V 24Cr 25Mn 26Fe 27Co 28Ni 29Cu 30Zn 39Y 40Zr 41Nb 42Mo 43Tc 44Ru
All transition metals

The story

What rhenium is, and how we found it

One of the rarest elements in the crust, and the metal that lets jet turbines run hotter.

The discovery of rhenium

The Last Great Element Hunt

Rhenium's discovery in 1925 marked the end of an era - it was the last stable element found in nature. This scientific detective story spans three decades, involves brilliant German chemists, and proves that persistence conquers even the most elusive targets in nature.

1905-1914: The Missing Element Mystery

Dmitri Mendeleev's periodic table predicted an element should exist between manganese and technetium, which he called "dvi-manganese." For 20 years, chemists worldwide searched frantically for this missing piece of the elemental puzzle, analyzing thousands of mineral samples without success.

False Alarms: Multiple "discoveries" proved false, including "nipponium" from Japan and "masurium" from Germany. Each failure deepened the mystery - where was element 75 hiding?

1922: The X-Ray Breakthrough

Henry Moseley's legacy guided the search. His X-ray crystallography work revealed that element 75 should produce characteristic X-ray emissions, providing a definitive identification method. This breakthrough gave chemists the tool they needed to find the needle in nature's haystack.

1925: The Triumph of the Noddacks

Walter and Ida Noddack along with Otto Berg achieved the impossible in Berlin (Physikalisch-Technische Reichsanstalt and Siemens & Halske). Working with platinum ores and columbite, they detected the telltale X-ray signature of element 75 using their important spectroscopic techniques.

The Challenge: Their first sample contained only 1 milligram of rhenium compounds extracted from over half a ton of ore - a concentration of 0.0002%. This makes finding a specific person in New York City look easy by comparison.

1928: Pure Metal Achievement

Three years after discovery, the Noddacks finally isolated 1 gram of pure rhenium metal through hydrogen reduction of ammonium perrhenate. This tiny sample, worth more than gold, proved rhenium's unique properties and launched decades of research into its applications.

The Scientific Heroes

Walter Noddack (1893-1960)

German analytical chemist who pioneered X-ray spectroscopy for element discovery. His meticulous approach and important techniques made rhenium's detection possible when others failed.

Ida Tacke-Noddack (1896-1978)

Brilliant German physicist and one of the first women to discover a chemical element, after Marie Curie and Lise Meitner. Her expertise in X-ray crystallography was crucial to rhenium's identification. In 1934 she also suggested that nuclei could split into large fragments, about five years before nuclear fission was confirmed.

Otto Berg (1874-1939)

German chemist specializing in rare element extraction. His chemical processing expertise enabled isolation of pure rhenium from very dilute ores.

Why Rhenium Was So Hard to Find

Rarity

At 0.7 parts per billion in Earth's crust, rhenium is virtually undetectable by conventional analysis. Most mineral samples contain no rhenium whatsoever.

Chemical Scattering

Rhenium doesn't form its own minerals but substitutes randomly for other elements at trace levels, preventing concentration in findable deposits.

Analytical Limits

1920s analytical chemistry couldn't detect sub-milligram quantities. Only X-ray spectroscopy provided sufficient sensitivity for rhenium detection.

Extraction Difficulty

Even after detection, extracting pure rhenium required processing enormous quantities of ore through dozens of chemical separation steps.

The Name "Rhenium"

The Noddacks chose "rhenium" to honor the Rhine River (Rhenus in Latin) flowing through their German homeland. This patriotic naming reflected the intense national pride in scientific achievement during the 1920s. Ironically, the Rhine River contains no detectable rhenium - the element is too rare even for the Rhine.

From Laboratory Curiosity to Space Age Essential

The Noddacks could never have imagined their laboratory curiosity would eventually power jet engines and enable space exploration. Their meticulous work identifying 1 milligram of rhenium compounds launched an industry now worth billions of dollars annually. Every commercial flight today depends on their 1925 breakthrough in a Berlin laboratory.

Scientific Legacy

Rhenium's discovery established analytical chemistry techniques still used today for trace element detection. The Noddacks' X-ray spectroscopy methods evolved into modern instruments capable of detecting individual atoms. Their persistence in pursuing the impossible continues to inspire scientists tackling today's most challenging research problems.

Applications

What rhenium is used for

Rhenium: A High-Temperature Metal

Rhenium stands as the rarest stable element on Earth, far rarer in the crust than gold or platinum, though much cheaper per kilogram. With high heat resistance and unique catalytic properties, this ultra-rare metal enables humanity's most demanding technologies.

Jet Engine Superalloys

Commercial aviation depends entirely on rhenium's ability to strengthen nickel superalloys in jet turbine blades. Operating at 1,600°C in screaming turbofan engines, rhenium-containing blades enable fuel efficiency that makes modern air travel economically viable. A single Boeing 777 engine contains 6 kg of rhenium.

Petroleum Refining Catalysts

Rhenium-platinum catalysts transformed gasoline production through catalytic reforming. These catalysts increase octane ratings while reducing harmful emissions, transforming crude oil into high-performance fuels. Every gallon of premium gasoline owes its quality to rhenium's catalytic activity.

Space Propulsion Systems

Spacecraft thrusters use rhenium's exceptional thermal shock resistance for high-temperature rocket thruster components. Rhenium maintains structural integrity during the large temperature cycling of space missions, from -270°C in Earth's shadow to +120°C in direct sunlight.

High-Temperature Thermocouples

Type C thermocouples using tungsten-rhenium alloys measure temperatures up to 2,320°C in aerospace testing, nuclear reactors, and materials research. These precision instruments monitor vacuum furnaces and hypersonic vehicle heat shields where other sensors would melt instantly.

Nuclear Technology

Rhenium's neutron absorption properties make it valuable for nuclear reactor control elements. Research reactors use rhenium alloys for components that must maintain strength under intense radiation while resisting neutron-induced embrittlement.

Advanced Research Applications

Electron microscopy filaments made from rhenium provide superior performance for ultra-high-resolution imaging. Scanning tunneling microscope tips use rhenium's atomically smooth surfaces to achieve high resolution in nanotechnology research.

Why Rhenium Commands Premium Prices

  • Rarity: Only 1 part per billion in Earth's crust - rarer than platinum, gold, and diamonds
  • Melting Point: Third-highest melting point (3,185°C) of all elements, surpassed only by tungsten and carbon
  • Catalysis: Platinum-rhenium catalysts reform petroleum fractions into high-octane gasoline
  • Strength Multiplier: Transforms brittle tungsten into ductile alloys while maintaining heat resistance
  • Corrosion Immunity: Resists attack by most acids, alkalis, and oxidizing environments

Strategic Economic Importance

Global rhenium mine production totals only about 81 tons annually (USGS, 2025). This scarcity keeps rhenium expensive, about $2,600 per kilogram on average in 2025 (USGS), yet airlines gladly pay these costs because rhenium-enhanced engines save millions in fuel efficiency and maintenance over their lifetimes.

Next-Generation Technologies

Fusion power reactors will require rhenium alloys for plasma-facing components that must survive neutron bombardment at 1,000°C. Hypersonic aircraft engines operating at Mach 5+ will depend on rhenium's thermal stability, while space elevators may use rhenium-strengthened carbon nanotube composites.

Rhenium: Hidden in Plain Sight

Despite being the rarest stable element, rhenium touches daily life through technologies that depend on its unusual properties. Most people benefit from rhenium without ever knowing it exists.

Commercial Aviation

  • Every Flight You Take: Commercial aircraft engines contain rhenium superalloys that enable safe, efficient flight. Without rhenium, modern aviation would be impossible - engines would fail from thermal stress
  • Fuel Efficiency: Rhenium-enhanced turbine blades run 100°C hotter than conventional alloys, improving fuel economy by 15% and reducing ticket prices
  • Engine Longevity: Rhenium prevents turbine blade cracking, extending engine life from 20,000 to 30,000+ flight hours
  • Military Aircraft: Fighter jets and transport planes rely on rhenium for high performance and reliability in combat conditions

Automotive Fuels

  • Premium Gasoline: Catalytic reforming with rhenium-platinum catalysts creates high-octane gasoline that prevents engine knock in performance vehicles
  • Cleaner Emissions: Rhenium catalysts reduce harmful aromatics in gasoline while maintaining engine performance
  • Racing Fuels: High-performance racing fuels achieve their octane ratings through rhenium-catalyzed refining processes
  • Jet Fuel: Aviation kerosene production uses rhenium catalysts to create thermally stable fuel for commercial and military aircraft

Industrial Processes

  • Steel Production: Some specialty steel alloys contain trace rhenium for high-temperature applications in power plants and chemical processing
  • Chemical Manufacturing: Pharmaceutical companies use rhenium catalysts to synthesize complex molecules for advanced medications
  • Electronics Testing: Semiconductor manufacturers use rhenium thermocouples to monitor ultra-high-temperature processes in chip fabrication

Space Technology

  • Satellite Communication: Rhenium components in satellite thrusters enable precise orbital positioning for GPS, weather forecasting, and telecommunications
  • Space Exploration: Mars rovers and deep space probes use rhenium alloys for components that must survive large temperature cycles
  • International Space Station: Life support and propulsion systems contain rhenium components for reliability in the harsh space environment

The Invisible Impact

You'll never see rhenium directly, but it enables the modern world:

  • Every commercial flight depends on rhenium-strengthened engines
  • Premium gasoline in your car was processed using rhenium catalysts
  • GPS satellites use rhenium thrusters to maintain precise orbits
  • Weather forecasts rely on satellites with rhenium components
  • International commerce depends on rhenium-enabled aviation and shipping

The Rarity Reality Check

Annual global rhenium production (about 81 tons in 2025) would fit in a small warehouse, yet this tiny amount enables:

  • 40,000+ commercial aircraft engines worldwide
  • Billions of gallons of refined gasoline annually
  • Thousands of satellites and space missions
  • Critical industrial processes worth trillions of dollars

Bottom line: Rhenium proves that even the rarest materials can have enormous impact when used strategically in high-value applications.

Where it comes from

Natural occurrence

7.00e-4 mg/kg of Earth's crust · more abundant than 31% of elements

Rhenium: A Widely Dispersed Element

Rarity in Numbers

Rhenium holds the crown as the rarest stable element in Earth's crust with an abundance of only 0.7 parts per billion. To grasp this rarity:

  • About 6 times rarer than gold
  • About 100 times rarer than silver
  • About 86,000 times rarer than copper
  • Rarer than many radioactive elements.

Analogy: If Earth's crust were a football stadium, rhenium would be equivalent to finding one specific grain of sand among all the seats.

The Last Element Standing

Rhenium was the last stable element discovered (1925), not because scientists weren't looking, but because it's virtually impossible to find. Even today, a century later, rhenium remains so rare that most geology students complete their degrees without ever seeing a pure sample.

Where Rhenium Hides

Molybdenum Ore Byproduct (95% of supply)

Rhenium doesn't form its own minerals in economic quantities. Instead, it substitutes for molybdenum in molybdenite (MoS₂) at levels of 0.001-0.2%. Every ton of molybdenum concentrate yields only 1-2 kg of rhenium after complex processing.

Copper Smelter Flue Dust (4% of supply)

Some copper ores contain trace rhenium that concentrates in smelter flue dust. Recovery requires processing thousands of tons of dust to extract kilograms of rhenium - like finding needles in haystacks.

Recycling (1% of supply)

Spent jet engine components undergo intensive recycling to recover every gram of rhenium. The metal's high value makes recycling economically attractive despite complex processing requirements.

Global Rhenium Production Centers

United States (about 12% of world production)

Sierrita Mine, Arizona: Freeport-McMoRan's copper-molybdenum operation is America's largest rhenium producer. The massive open-pit mine processes 100 million tons of ore annually and recovers rhenium from its molybdenum concentrates.

Chile (about 37% of world production)

Chuquicamata & El Teniente: These giant copper mines in the Andes Mountains contain Chile's rhenium resources. High-altitude mining operations extract rhenium from molybdenum concentrates in some of the world's largest mining complexes.

Poland (about 12% of world production)

KGHM Copper Belt: Poland's ancient copper deposits contain trace rhenium recovered from copper smelting operations. This European source provides strategic supply diversity for aerospace manufacturers.

Other Sources (about 40%)

China (about 25% of 2025 output), Uzbekistan, South Korea, Kazakhstan and Armenia contribute the rest from copper and molybdenum operations. Every producing country guards their rhenium as a strategic resource.

How Nature Creates Rhenium

Rhenium's rarity stems from its formation requirements:

  • Stellar Nucleosynthesis: Rhenium forms only in the most violent stellar explosions, making it cosmically rare from the start
  • Geochemical Behavior: Rhenium's chemistry causes it to scatter rather than concentrate, preventing rich ore formation
  • Late Crystallization: During magma cooling, rhenium enters the last-formed minerals at trace levels, never achieving high concentrations
  • Weathering Mobility: Unlike gold or platinum, rhenium doesn't survive weathering to form placer deposits

The Extraction Challenge

Extracting rhenium requires processing enormous quantities of host materials:

  • 1 million tons of molybdenum ore → 1 ton of rhenium
  • 20 processing steps including roasting, leaching, and precipitation
  • 99.99% purity required for aerospace applications
  • $50 million investment minimum for new rhenium recovery facility

Strategic Supply Concerns

Rhenium's scarcity creates supply chain vulnerabilities:

  • Three countries control 75% of global production
  • No substitute exists for critical aerospace applications
  • Annual production could fit in a single shipping container
  • Strategic stockpiles are classified national security information
  • Prices have ranged from about $1,000 to $2,600 per kilogram in 2021-2025, after an all-time high near $10,600 in 2008

Handling

Safety

Rhenium Safety Information

Overall Safety Rating: LOW RISK

Rhenium metal and most rhenium compounds have low toxicity and present minimal health hazards under normal handling conditions. However, its high value and specialized applications require specific safety protocols to prevent loss and ensure worker protection.

Physical Handling Safety

  • Material Value: At about $2,600/kg (2025 average), rhenium requires secure handling procedures to prevent loss. Use containment systems and accounting protocols for all rhenium materials
  • Powder Form: Fine rhenium powder is a flammable solid. Store under inert atmosphere and avoid static electricity buildup that could cause ignition
  • Sharp Edges: Machined rhenium components can have extremely sharp edges due to the metal's hardness. Use appropriate cut-resistant gloves when handling fabricated parts
  • High Density: Rhenium's density (21.0 g/cm³) makes small pieces surprisingly heavy. Use proper lifting techniques to prevent injury

Inhalation Considerations

  • Metal Dust: Rhenium metal dust has low toxicity but may cause respiratory irritation with prolonged exposure. Use local exhaust ventilation when machining or grinding
  • Compound Vapors: Some rhenium compounds (rhenium heptoxide) can be irritating to respiratory system. Handle in well-ventilated areas or fume hoods
  • Welding/Processing: High-temperature processing may generate metal fumes. Use appropriate respiratory protection and maintain good ventilation

Chemical Safety

  • Rhenium Heptoxide (Re₂O₇): Volatile and potentially irritating. Handle with chemical gloves in fume hood to avoid skin and eye contact
  • Ammonium Perrhenate: Generally safe but may cause mild irritation. Standard laboratory precautions are sufficient
  • Acid Compatibility: Rhenium dissolves in nitric acid and hydrogen peroxide, producing potentially hazardous solutions. Use proper chemical handling procedures
  • Oxidizing Conditions: Rhenium can form volatile oxides at high temperatures in air. Control heating conditions to prevent unexpected vapor formation

Emergency Response

Eye Contact

Flush immediately with clean water for 15 minutes. Remove contact lenses if present and easily removable. Seek medical attention if irritation persists or for chemical compound exposure.

Skin Contact

Wash with soap and water. Rhenium metal is generally non-irritating to skin. For chemical compounds, remove contaminated clothing and flush affected area thoroughly.

Inhalation

Move to fresh air. Rhenium has low inhalation toxicity, but seek medical attention if respiratory symptoms develop or for large exposures to compounds.

Fire Response

Rhenium metal is not combustible, but fine powders may burn. Use Class D fire extinguisher for metal fires. Water may spread burning metal particles.

Industry-Specific Precautions

Aerospace Manufacturing

Jet engine component fabrication requires clean room protocols to prevent contamination. Trace impurities can compromise rhenium's performance in superalloy applications.

Catalyst Production

Catalyst preparation involves potentially hazardous solvents and reducing agents. Follow petroleum industry safety protocols for catalyst handling and regeneration.

Research Applications

High-temperature experiments with rhenium require specialized safety equipment. Monitor for formation of volatile oxides in oxidizing atmospheres above 400°C.

Recommended Protective Equipment

  • Respiratory Protection: N95 respirator for dust operations, full-face respirator for chemical compound handling
  • Eye Protection: Safety glasses minimum, chemical goggles for compound handling, face shield for high-temperature operations
  • Hand Protection: Nitrile gloves for routine handling, cut-resistant gloves for sharp components, chemical-resistant gloves for compounds
  • Body Protection: Laboratory coat or coveralls, steel-toed shoes for heavy components

Storage & Handling Requirements

  • Secure Storage: Store rhenium in locked, fireproof safes due to high value. Maintain detailed inventory records for tracking
  • Environmental Control: Keep in dry environment to prevent oxidation. Store powders under inert atmosphere (argon or nitrogen)
  • Segregation: Separate from strong acids and oxidizing agents that could cause unwanted reactions
  • Temperature Control: Avoid storage above 400°C where volatile oxide formation becomes significant
  • Waste Management: All rhenium waste must be collected for recycling due to economic value. No disposal to normal waste streams permitted

Keep exploring

Use rhenium in the tools

Quick answers

Rhenium: common questions

What is rhenium?

Rhenium (symbol Re) is element 75 on the periodic table, a transition metal in period 6, group 7. One of the rarest elements in the crust, and the metal that lets jet turbines run hotter. At room temperature it is a solid.

What is the electron configuration of rhenium?

Rhenium's ground-state electron configuration is [Xe] 4f¹⁴ 5d⁵ 6s², giving 6 occupied shells with the distribution 2, 8, 18, 32, 13, 2.

What are the melting and boiling points of rhenium?

Rhenium melts at 3459 K (3185.9 °C) and boils at 5869 K (5595.9 °C). That puts it among the most refractory elements — it stays solid at temperatures that vaporise most metals.

What is the atomic mass of rhenium?

The standard atomic weight of rhenium is 186.207 u. That is a weighted average across its naturally occurring isotopes, which is why it is rarely a whole number.

How many neutrons does rhenium have?

The most common rhenium atom, Re-187, has 112 neutrons: its mass number, 187, minus its atomic number, 75. It makes up 62.60% of natural rhenium. The classroom shortcut, rounded atomic mass (186.207) minus atomic number, gives 111 instead, because the atomic mass is an average over all natural isotopes of rhenium.

How dense is rhenium?

Rhenium has a density of 21.02 g/cm³. Water is 1.0 g/cm³, so a block of rhenium is about 21× heavier.

What is the electronegativity of rhenium?

Rhenium has a Pauling electronegativity of 1.9. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). Values in this middle band tend to form covalent rather than strongly ionic bonds.

Who discovered rhenium, and when?

Rhenium was discovered in 1925 by Noddack, Tacke & Berg. Origin of the name: Latin Rhenus, the river Rhine.

How common is rhenium on Earth?

Rhenium makes up about 7.00e-4 mg/kg of the Earth's crust — genuinely rare, which is why it is expensive.

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