Ruthenium (Ru)

Ruthenium is a chemical element with the atomic number 44 in the periodic table. Its abundance in Earth’s crust is calculated to be 0.0001 ppm. 

Element 44 is a rare transition metal classified in the platinum family of elements. This very rare noble metal has only one valence electron which makes ruthenium inert to most of the other chemicals. Nowadays, ruthenium is extensively used in electronics, but the ongoing clinical trials bring hope that ruthenium could have a future use in anti-cancer therapy as a new-generation organometallic drug.

Chemical and Physical Properties of Ruthenium

Atomic Number44
Group8 (Transition metals)
Atomic Weight101.07
Orbitals[Kr] 4d7 5s1
Ionic Radius.62 (+4) Å
Discovered ByJędrzej Śniadecki (1808), Karl Ernst Claus (1884)
Year1808, 1884
Density12.1 at 20°C
DescriptionA silvery-white metal
Physical StateSolid at room temperature
Half-lifeFrom 50# milliseconds [>1.5 µs] to 373.59(15) days
Density12.1 at 20°C
Melting Point2333°C, 4231°F, 2606 K
Boiling Point4147°C, 7497°F, 4420 K
Van der Waals Radius0.135 nm
Most Characteristic Isotope101Ru, 102Ru, 104Ru
The Energy of the First Ionization722.4 kJ.mol-1
The Energy of the Second Ionization1620 kJ.mol-1
The Energy of the Third Ionization2747 kJ.mol-1
Discovery Date1808 by Jędrzej Śniadecki, 1884 by Karl Ernst Claus

With the periodic table symbol Ru, atomic number 44, atomic mass of 101.07 g.mol-1, and electron configuration [Kr] 4d75s1, ruthenium is a very hard, brittle, silvery-white metal substance that is classified as a transition metal. 

Ruthenium reaches its boiling point at 4147°C, 7497°F, 4420 K, while the melting point is achieved at 2333°C, 4231°F, 2606 K. This member of the platinum group of elements in the periodic table has an electronegativity of 2.2 according to Pauling, whereas the atomic radius according to van der Waals is 0.135 nm. 

Similarly to all other platinum group metals, ruthenium also has excellent anti-corrosive properties. This rather inert chemical element does not react with acids, water, and air, even with aqua regia.

How Was Ruthenium Discovered?

The story of ruthenium’s discovery begins in 1807, when the Polish chemist and physician Andrew Sniadecki (orig. Jedrzej Sniadecki) thought he had discovered a new metal in a platinum ore he was analysing. He named the new substance “vestium”. However, since all his fellow colleagues’ efforts to reproduce Sniadecki’s experiment failed, the Polish chemist gave up on further analysis of the substance.

Twenty years later, 1828, the Swedish chemist Jons Jacob Berzelius and Russian chemist Gottfried W. Osann tried to dissolve the crude platinum ores in aqua regia, after which they dedicated their time to analysing the residues of this process. Ossan was convinced that there are not one, but three new elements in the substance. He labeled them as pluranium, polonium, and ruthenium. 

His colleague, however, was not so enthusiastic about these results. Berzelius considered that more chemical analyses are needed for the scientific evidence derived by Ossan to be validated. 

This sparked the scientific interest of the Russian chemist Karl Karlovich Klaus (1796-1864). Klaus revised the possibility of a new metal contained in the platinum ores obtained from the Ural Mountains. 

In 1844, in Kazan, Russia, Karl K. Klaus first attempted to reproduce Snaidecki’s experiment. For this, he first isolated the salt (ammonium chlororuthenate, (NH4)2RuCl6) in which he observed the occurrence of the new metal. With an additional effort, Klaus succeeded in isolating the ruthenium metal from the platinum ore. This Russian scientist is also credited as the first scientist to determine the chemical properties of this new transition metal. 

How Did Ruthenium Get Its Name?

Element 44 got its name from the Latin word ‘Ruthenia’ meaning Russia. This relates to the fact that the platinum ores in which ruthenium is traced were originally obtained from the Ural Mountains in Russia. The name of this chemical element is also a nod to the home country of its discoverer. 

Where Can You Find Ruthenium?

Ruthenium naturally occurs in platinum ores. It’s mainly found in the mineral laurite that can be frequently traced along the minerals cooperite, osmiridium, pentlandite, sperrylite, chrominte, and braggite. It also can be obtained from the minerals that contain the other platinum group elements. 

Element 44 is primarily obtained as a byproduct of mining and refining platinum, as well as a byproduct of nickel mining from the mineral deposits located in the Sudbury region of Ontario, Canada. The largest deposits in the world of this rare-earth metal are found in South Africa, Canada, South America, and the Ural Mountains, Russia. 

Ruthenium in Everyday Life

Ruthenium metal is especially demanded by the electronic and the chemical industry, but it can be also used in medicine:

  • The synthetically produced RuS2 is a highly active catalyst for hydrodesulfurization, i.e. the process of sulfur dioxide (SO2) reduction from the petroleum products, such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils;
  • Ruthenium tetroxide is used as a staining agent electron microscopy of polymers that improves the image contrast, as well as a fixative for biological samples;
  • Due to its strong anticorrosive properties, ruthenium is chiefly used as an alloying agent. By adding even small amount of ruthenium to an alloy, element 44 acts as hardener of the compound;
  • Ruthenium oxides can be applied as versatile catalysts;
  • In combination with other elements, such as bismuth, titanium, palladium and platinum, ruthenium can be used in crisp resistors, in solar cells, and electrical contacts. It not only increases the wear resistance on electrical components, but it also adds to the anti-corrosiveness;
  • A ruthenium-molybdenum alloy is considered as a superconductor when exposed to temperature of 10.6 K (-440.6 F / -262.5°C);
  • Chemical industry applies ruthenium as a coat of the anodes of electrochemical cells used in chlorine production;
  • Ruthenium alloys are often used for tipping of the fountain pen nibs;
  • Ruthenium(VIII) oxide and ruthenium dioxide are employed in the production of many electronic components, such as potentiometers and resistors. 

How Dangerous Is Ruthenium?

Ruthenium tetroxide (RuO4) is an extremely toxic substance that is considered as a potential carcinogen. This golden-yellow, volatile, solid ruthenium compound penetrates the tissues and reacts strongly with proteins, glycogen, and monosaccharides. Since it strongly stains the skin, it’s considered as a possible carcinogen substance. 

On the other hand, elemental ruthenium has a good reputation in medicine. While other metals are highly toxic for our body, the pure ruthenium metal actually has the ability to eliminate the metal toxicity by acting as a blocking agent. This prevents the spread of metal in the body that may trigger adverse health effects. 

The newest research on anticancer drugs show the beneficial side of this chemical element when used in anticancer treatments

Ruthenium Anticancer Drugs

Some of the recent clinical trials point out that ruthenium complexes display anticancer properties that might be a good alternative to the platinum-based anti-cancer drugs. 

While the chemotherapeutic use of platinum complexes often trigger side effects such as nerve damage, hair loss and nausea, fewer and less severe side effects have been observed after the therapeutic administration of the ruthenium complexes.  

Environmental Effects of Ruthenium

The pure, elemental form of ruthenium has no negative impact on the environment. However, one of the longest living ruthenium radioisotopes (106Ru)  is included in atmospheric testing of nuclear weapons.

The radioactive particles produced during these nuclear tests contaminate all spheres of our planet, which ultimately lead to increased risk of developing cancer in humans, or even a complete extinction of the other living organism in the environment. 

Isotopes of Ruthenium

There are 34 ruthenium isotopes, with atomic masses tanging from ruthenium-87 to ruthenium-120. Among them, 27 radioactive forms of this chemical element have been observed. 

Pure ruthenium is composed of several isotopes: Ru-100, Ru-101, Ru-102, and Ru-104. Ruthenium-102 form is the most abundant form of element 44. 

With a half-life of 373.59 days, 106Ru is the most stable radioisotope of ruthenium. Ruthenium isotopes decay via electron capture and beta emission mode to technetium and rhodium.  


[n 1]

ZNIsotopic mass (Da)

[n 2][n 3]


[n 4]



[n 5]



[n 6]

Spin and


[n 7][n 4]

Natural abundance (mole fraction)
Excitation energy[n 4]Normal proportionRange of variation
87Ru444386.94918(64)#50# ms [>1.5 µs]β+87Tc1/2−#  
88Ru444487.94026(43)#1.3(3) s [1.2(+3−2) s]β+88Tc0+  
89Ru444588.93611(54)#1.38(11) sβ+89Tc(7/2)(+#)  
90Ru444689.92989(32)#11.7(9) sβ+90Tc0+  
91Ru444790.92629(63)#7.9(4) sβ+91Tc(9/2+)  
92Ru444891.92012(32)#3.65(5) minβ+92Tc0+  
93Ru444992.91705(9)59.7(6) sβ+93Tc(9/2)+  
94Ru445093.911360(14)51.8(6) minβ+94Tc0+  
95Ru445194.910413(13)1.643(14) hβ+95Tc5/2+  
96Ru445295.907598(8)Observationally Stable[n 8]0+0.0554(14) 
97Ru445396.907555(9)2.791(4) dβ+97mTc5/2+  
101Ru[n 9]4457100.9055821(22)Stable5/2+0.1706(2) 
102Ru[n 9]4458101.9043493(22)Stable0+0.3155(14) 
103Ru[n 9]4459102.9063238(22)39.26(2) dβ103Rh3/2+  
104Ru[n 9]4460103.905433(3)Observationally Stable[n 10]0+0.1862(27) 
105Ru[n 9]4461104.907753(3)4.44(2) hβ105Rh3/2+  
106Ru[n 9]4462105.907329(8)373.59(15) dβ106Rh0+  
107Ru4463106.90991(13)3.75(5) minβ107Rh(5/2)+  
108Ru4464107.91017(12)4.55(5) minβ108Rh0+  
109Ru4465108.91320(7)34.5(10) sβ109Rh(5/2+)#  
110Ru4466109.91414(6)11.6(6) sβ110Rh0+  
111Ru4467110.91770(8)2.12(7) sβ111Rh(5/2+)  
112Ru4468111.91897(8)1.75(7) sβ112Rh0+  
113Ru4469112.92249(8)0.80(5) sβ113Rh(5/2+)  
114Ru4470113.92428(25)#0.53(6) sβ (>99.9%)114Rh0+  
β, n (<.1%)113Rh
115Ru4471114.92869(14)740(80) msβ (>99.9%)115Rh   
β, n (<.1%)114Rh
116Ru4472115.93081(75)#400# ms [>300 ns]β116Rh0+  
117Ru4473116.93558(75)#300# ms [>300 ns]β117Rh   
118Ru4474117.93782(86)#200# ms [>300 ns]β118Rh0+  
119Ru4475118.94284(75)#170# ms [>300 ns]     
120Ru4476119.94531(86)#80# ms [>300 ns]  0+  

Source: Wikipedia

List of Ruthenium Compounds 

Ruthenium has a hexagonal close-packed crystal structure and typically adopts the oxidation state of +2, +3, and +4 in a compound. When exposed to air, water, or  acid, element 44 does not form any chemical reaction. Only molten alkali and halogens trigger a chemical reaction of ruthenium. 

Some of the most frequently prepared ruthenium compound include:

  • Diruthenium tetraacetate chloride
  • Lithium ruthenate
  • Ruthenium anticancer drugs
  • Ruthenium boride
  • Ruthenium hexafluoride
  • Ruthenium pentafluoride
  • Ruthenium tetroxide
  • Ruthenium(III) acetate
  • Ruthenium(III) chloride
  • Ruthenium(IV) oxide
  • Strontium ruthenate
  • Tetrapropylammonium perruthenate
  • Uranium ruthenium silicide

5 Interesting Facts and Explanations

  1. Platinum metals are considered to be somewhat rare, noble, and valuable substances. They characterize with high melting points, boiling points, and densities, as well as with bright and shiny polish of their metal form. 
  2. Ruthenium is discovered as the last chemical element classified in the platinum metals group (PMG). 
  3. Discovered in 1866 in Borneo, Malaysia, by the American chemist Charles A. Joy, laurite RuS2 is an opaque black, metallic ruthenium sulfide mineral that may also contain traces of the elements osmium, iridium, rhodium, and iron.
  4. There are two ruthenium compounds that are currently undergoing clinical evaluation as anti-cancer drugs – NAMI{Na[trans-RuCl4](DMSO)(imida)]} and NAMI-A {H2Im[trans-RuCl4(DMSO)HIm[imidH]. So far, no ruthenium complexes have been approved by the American Food and Drugs Administration (FDA). 
  5. When released during a nuclear accident, the radioactive isotopes of ruthenium 103Ru and 106Ru are considered the second most hazardous gaseous isotopes after the iodine-131 isotope.