44 Ru Ruthenium 101.07
Transition metal d-block Period 5 Group 8

Ruthenium

Ru · Element 44 · Iron group

A platinum-group metal that hardens its neighbours and catalyses ammonia synthesis.

STATE AT 20°C Solid
ATOMIC MASS 101.07 u
ELECTRON CONFIGURATION [Kr] 4d⁷ 5s¹

Structure

The ruthenium 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 ruthenium sits among all 118 elements for that property.

Physical

Density 12.45 g/cm³ 74%
Melting point 2607 K 93%
Boiling point 4423 K 89%
Specific heat 0.238 J/g·K
Thermal conductivity 117 W/m·K 88%

Atomic

Atomic radius 134 pm 21%
Covalent radius 146 pm
Van der Waals radius 207 pm

Electronic

Electronegativity 2.2 78%
Ionisation energy 710.1 kJ/mol 51%
Electron affinity 101.3 kJ/mol 76%

Occurrence

Abundance in crust 0.001 mg/kg 32%

Identity

SymbolRu
Atomic number44
Atomic mass101.07 u
CategoryTransition metal
Blockd
Crystal structurehexagonal close-packed
Oxidation states-2, 0, +1, +2, +3, +4, +5, +6, +7, +8
Discovered1844
Discovered byKarl Ernst Klaus

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

Size, to scale

How big is a ruthenium atom?

Radius 134 pm — that is 0.134 nm, so about 3731 million of them side by side would span a millimetre.

Thermal range

Solid, liquid, gas — and when

Ruthenium is liquid over a 1816 K window, from 2607 K to 4423 K.

Where it sits

Position in the table

Ruthenium sits in period 5, group 8. Everything in group 8 shares the same outer-electron count, which is why they behave so similarly.

OTHER TRANSITION METALS

All transition metals

The story

What ruthenium is, and how we found it

A platinum-group metal that hardens its neighbours and catalyses ammonia synthesis.

The discovery of ruthenium

Discovery Story

The Polish Chemist's Quest

The discovery of ruthenium in 1844 represents one of chemistry's most persistent detective stories, solved by Polish chemist Karl Ernst Claus at the University of Kazan in Russia. Claus's methodical approach and chemical intuition led him to identify the fourth member of what we now call the platinum group metals.

Earlier Attempts and False Claims

The story begins in 1827 when Gottfried Osann, a German chemist, claimed to have discovered three new elements in platinum ores from the Ural Mountains. He named them pluranium, ruthenium, and polinium. However, Osann's chemical techniques were insufficient to properly isolate and characterize these proposed elements, and his claims were met with skepticism from the scientific community.

Jöns Jacob Berzelius, the renowned Swedish chemist, investigated Osann's claims in 1828 but concluded that the supposed new elements were actually mixtures of known platinum group metals with silica and other impurities. This setback discouraged further research into potential new platinum group elements for over a decade.

Claus's Breakthrough

Karl Claus approached the problem with superior analytical techniques and unwavering patience. Working with platinum ore residues that remained after extracting platinum, palladium, rhodium, and iridium, Claus suspected additional elements might be hiding in the complex mixture.

Through painstaking chemical separations involving multiple acid treatments, precipitation reactions, and crystallization steps, Claus gradually isolated a new substance with properties distinct from all known elements. He obtained the element in pure metallic form and carefully characterized its chemical and physical properties.

Naming and Recognition

Claus chose the name "ruthenium" from "Ruthenia," the Latin name for Russia, honoring his adopted homeland where he conducted his research. This naming also connected the element to its discovery location in Russian platinum ores.

The scientific community initially greeted Claus's announcement cautiously, given the earlier false claims. However, his meticulous documentation and the reproducibility of his results soon convinced skeptics. Other chemists confirmed his findings by following his detailed procedures and obtaining identical results.

Legacy and Impact

Claus's discovery completed the identification of six platinum group metals (platinum, palladium, rhodium, iridium, osmium, and ruthenium) that naturally occur together. His work demonstrated the importance of patient, systematic analysis in identifying new elements from complex natural mixtures.

The discovery had profound implications for understanding atomic structure and chemical periodicity. Ruthenium's position in the periodic table helped validate Dmitri Mendeleev's periodic law and provided insights into the electronic structure of transition metals.

Modern Significance

Today, we recognize Claus's discovery as foundational to the electronics industry. Without ruthenium, modern data storage, advanced catalysis, and precision electronics would be impossible. His patient chemical detective work in 1844 enabled technologies that define our digital age.

Applications

What ruthenium is used for

Industrial Applications

Ruthenium stands as one of the most technologically important platinum group metals, with applications spanning from cutting-edge electronics to life-saving medical devices. Its exceptional resistance to corrosion and unique catalytic properties make it central in modern industry.

Electronics and Data Storage

The electronics industry consumes the largest portion of ruthenium production. Hard disk drives rely on ruthenium-based magnetic layers for ultra-high-density data storage. These thin films, often just a few atoms thick, enable modern computers to store terabytes of information in compact spaces. Ruthenium's magnetic properties and chemical stability make it irreplaceable in this application.

Resistor manufacturing utilizes ruthenium oxide (RuO₂) to create thick-film resistors found in virtually every electronic device. These resistors provide precise electrical resistance values crucial for proper circuit function in smartphones, computers, and industrial equipment.

Chemical Catalysis

Ruthenium-based catalysts drive critical industrial processes. In ammonia synthesis, ruthenium catalysts offer superior performance to traditional iron catalysts, operating at lower pressures and temperatures while achieving higher conversion rates. This advancement could revolutionize fertilizer production, potentially feeding billions more people.

The Fischer-Tropsch process uses ruthenium catalysts to convert synthesis gas (carbon monoxide and hydrogen) into liquid hydrocarbons, providing a pathway to produce clean fuels from coal, natural gas, or biomass. This technology becomes increasingly important as nations seek energy independence and cleaner fuel alternatives.

Advanced Materials

Ruthenium alloys enhance the properties of other metals dramatically. Titanium-ruthenium alloys combine titanium's lightweight properties with ruthenium's corrosion resistance, creating materials ideal for aerospace applications, chemical processing equipment, and medical implants that must function in harsh biological environments for decades.

Electrical contacts in high-performance switches and relays incorporate ruthenium to prevent corrosion and ensure reliable electrical connections even after millions of switching cycles. These components are critical in automotive electronics, industrial control systems, and telecommunications equipment.

Emerging Technologies

Research into solar cell technology shows ruthenium-based dyes significantly improving efficiency in dye-sensitized solar cells. These cells could provide cost-effective solar energy solutions for developing nations and remote locations where traditional silicon panels are impractical.

Cancer treatment applications utilize ruthenium complexes as chemotherapy drugs that target cancer cells more precisely than traditional platinum-based treatments, potentially reducing side effects while improving cure rates.

Everyday Applications

Consumer Electronics

Every smartphone, laptop, and tablet contains ruthenium in its hard drive magnetic storage layers. When you save a photo, download an app, or store music, you're relying on ruthenium's magnetic properties to preserve that data reliably for years.

Electronic resistors containing ruthenium oxide regulate electrical current in virtually every electronic device. From the charging circuit in your phone to the power management system in your car, these tiny components ensure safe and efficient operation.

Automotive Technology

Modern vehicles increasingly use ruthenium-enhanced electrical contacts in critical systems like fuel injection controls, anti-lock braking systems, and engine management computers. These contacts must function reliably through extreme temperature variations and millions of switching cycles over a vehicle's lifetime.

Industrial Equipment

Chemical processing equipment in industries producing plastics, pharmaceuticals, and specialty chemicals relies on ruthenium's exceptional corrosion resistance. Reactor vessels and piping systems coated with ruthenium-containing alloys can handle the most aggressive chemical environments without degradation.

High-performance electrical switches in power plants, manufacturing facilities, and data centers use ruthenium-based contacts to ensure reliable operation even when switching high voltages and currents thousands of times daily.

Scientific Instruments

Laboratory equipment and analytical instruments frequently incorporate ruthenium electrodes for their chemical inertness and electrical properties. These electrodes enable precise measurements in research that advances medicine, materials science, and environmental monitoring.

Specialized Applications

Fountain pen nibs on premium writing instruments often feature ruthenium plating for its hardness and corrosion resistance, ensuring smooth writing performance for decades. Luxury jewelry incorporates ruthenium plating to create striking black finishes that resist tarnishing and wear.

Where it comes from

Natural occurrence

0.001 mg/kg of Earth's crust · more abundant than 32% of elements

Natural Distribution

Crustal Abundance and Rarity

Ruthenium ranks among Earth's rarest elements, with an average crustal abundance of only 0.001 parts per million (1 ppb). To put this extreme rarity in perspective, you would need to process approximately 100 million tons of average crustal rock to extract just one kilogram of ruthenium. This scarcity makes ruthenium roughly 10,000 times rarer than gold.

Primary Deposits

The world's most significant ruthenium deposits occur in South Africa's Bushveld Complex, a massive layered igneous intrusion that formed 2 billion years ago. This geological formation contains the world's largest reserves of platinum group metals, with ruthenium concentrated in specific layers alongside platinum, palladium, and rhodium.

Russia's Norilsk region provides another major source, where ruthenium occurs in copper-nickel sulfide ores formed by ancient volcanic activity. The harsh Arctic conditions make extraction challenging, but the high metal concentrations justify the effort.

Canada's Sudbury Basin, created by a massive meteorite impact 1.85 billion years ago, contains significant ruthenium deposits associated with nickel and copper ores. The impact event concentrated these metals through unique geological processes impossible to replicate.

Geological Formation

Ruthenium's extreme rarity results from its siderophile nature - it preferentially bonds with iron and sank toward Earth's core during planetary formation. Most ruthenium now accessible at the surface arrived through later geological processes: volcanic activity bringing deep materials upward, meteorite impacts, and hydrothermal circulation.

Platinum group metals, including ruthenium, often occur together in layered igneous complexes where slow cooling allowed different minerals to crystallize in distinct layers. These formations represent some of Earth's most economically important geological features.

Cosmic Origins

Ruthenium forms through neutron capture processes in dying stars, particularly during supernova explosions. The element's nuclear structure requires the extreme conditions found only in stellar cores and explosive stellar events. Earth's ruthenium inventory represents the accumulated debris from countless ancient supernovae that enriched the solar nebula before our planet formed.

Extraction Challenges

Ruthenium extraction involves processing enormous quantities of ore - typically 10-20 tons of ore yield just one ounce of ruthenium. The complex metallurgical processes required make ruthenium one of the most expensive elements to produce, contributing to its high market value and driving recycling efforts.

Handling

Safety

Safety Information

General Toxicity Profile

Ruthenium metal poses minimal health risks in its pure metallic form. The bulk metal is chemically inert under normal conditions and presents primarily physical hazards from sharp edges or impact injuries during handling.

Chemical Compound Hazards

Ruthenium compounds vary significantly in toxicity. Ruthenium tetroxide (RuO₄) presents the greatest danger - this volatile compound can cause severe respiratory irritation and chemical burns. It's particularly hazardous because it readily penetrates skin and mucous membranes.

Ruthenium chlorides and other salts can cause skin and eye irritation. Prolonged exposure may lead to allergic sensitization, making future exposures more dangerous even at lower concentrations.

Workplace Safety Protocols

Personal Protective Equipment (PPE): Always wear nitrile or neoprene gloves when handling ruthenium compounds. Standard latex gloves provide insufficient protection. Use safety glasses with side shields and work in well-ventilated areas or fume hoods.

Dust control measures are critical when handling powdered ruthenium or its compounds. Use HEPA filtration systems and avoid creating airborne particles through grinding, cutting, or vigorous mixing.

First Aid Procedures

Skin contact: Remove contaminated clothing immediately and flush affected areas with copious amounts of water for at least 15 minutes. Seek medical attention if irritation persists or if exposure involved concentrated solutions.

Eye contact: Flush eyes with clean water for at least 15 minutes, holding eyelids open to ensure thorough rinsing. Remove contact lenses if present and easily removable. Seek immediate medical attention.

Inhalation: Move to fresh air immediately. If breathing difficulties occur, seek emergency medical treatment. Ruthenium tetroxide exposure requires immediate medical intervention.

Storage and Disposal

Storage requirements: Keep ruthenium compounds in tightly sealed containers away from moisture, acids, and oxidizing agents. Store in cool, dry locations with appropriate secondary containment.

Waste disposal: Due to ruthenium's high value, most facilities recover and recycle ruthenium-containing waste. Contact specialized precious metal reclaimers rather than disposing as hazardous waste. Never dispose of ruthenium compounds in regular trash or down drains.

Quick answers

Ruthenium: common questions

What is Ruthenium?

Ruthenium (symbol Ru) is element 44 on the periodic table, a transition metal in period 5, group 8. A platinum-group metal that hardens its neighbours and catalyses ammonia synthesis. At room temperature it is a solid.

What is the electron configuration of Ruthenium?

Ruthenium's ground-state electron configuration is [Kr] 4d⁷ 5s¹, giving 5 occupied shells holding 2, 8, 18, 15, 1 electrons respectively.

What are the melting and boiling points of Ruthenium?

Ruthenium melts at 2607 K (2333.9 °C) and boils at 4423 K (4149.9 °C). That puts it among the most refractory elements — it stays solid at temperatures that vaporise most metals.

What is the atomic mass of Ruthenium?

The standard atomic weight of Ruthenium is 101.07 u. That is a weighted average across its naturally occurring isotopes, which is why it is rarely a whole number.

How dense is Ruthenium?

Ruthenium has a density of 12.45 g/cm³. Water is 1.0 g/cm³, so a block of ruthenium is about 12.5× heavier.

What is the electronegativity of Ruthenium?

Ruthenium has a Pauling electronegativity of 2.2. 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 Ruthenium, and when?

Ruthenium was discovered in 1844 by Karl Ernst Klaus. It is named after latin Ruthenia, Russia.

How common is Ruthenium on Earth?

Ruthenium makes up about 0.001 mg/kg of the Earth's crust — genuinely rare, which is why it is expensive.