Average mass of an atom in unified atomic mass units (1 u is 1/12 of the mass of a carbon-12 atom). Accounts for the natural mix of the element’s isotopes.
Number of the vertical column, 1 to 18 in IUPAC numbering. Elements in a group share the same outer-shell layout, so their properties are alike.
Number of the horizontal row. Usually equal to the number of electron shells in the atom; palladium is the exception, with four shells in period 5.
The subshell (s, p, d or f) that receives the last electrons in the usual filling order; it divides the table into four blocks. Real atoms sometimes differ: lanthanum starts the f-block but has no f electrons.
[Kr] 5s¹ 4d⁷
How electrons are arranged in subshells. The bracket stands for the previous noble gas; the superscript is the number of electrons in a subshell.
2, 8, 18, 15, 1
Number of electrons in each shell, from the nucleus outwards.
2,334 °C (2,607 K)
Temperature at which the solid turns liquid at standard pressure. Helium, carbon and arsenic do not melt at normal pressure: helium needs about 25 atm, carbon and arsenic turn straight into vapour.
4,150 °C (4,423 K)
Temperature at which the liquid boils at standard pressure. For carbon and arsenic, the temperature at which the solid turns straight into vapour (sublimation).
12.1 g/cm³
Mass of one cubic centimetre of the substance. For gases, at 0 °C and standard pressure.
2.2 Pauling
How strongly an atom pulls electrons towards itself in a chemical bond. On the Pauling scale it runs from 0.79 for caesium to 3.98 for fluorine.
7.361 eV
Energy needed to remove the most loosely bound electron from an atom. The lower it is, the more easily the element gives up an electron, which is typical of metals.
1.046 eV
Energy released when a neutral atom gains an electron. Highest for the halogens. Noble gases, nitrogen and some metals form no stable negative ion.
146 pm
Half the length of a single covalent bond between two atoms of the element. It shows the size of an atom inside a molecule or crystal: 76 pm for carbon, 132 pm for iron.
+4, +3
Charges the atom would have in its compounds if all its bonds were ionic; the main ones are listed.
Ruthenium (Ru) is a chemical element with atomic number 44. It sits in group 8 and period 5 of the periodic table, in the d-block. It is a transition metal. At room temperature it is a solid. Its standard atomic weight is 101.07.
Origin of the name
Ruthenium is named after Russia, in Latin Ruthenia. Karl Klaus discovered it in 1844 at Kazan University, in the residues left after platinum ore from the Urals had been dissolved in aqua regia. Others had come close before him: Gottfried Osann reported it in an impure state, and in 1808 the Polish chemist Jędrzej Śniadecki announced an element he called vestium, after the asteroid Vesta, but withdrew the claim when others could not repeat his results.
Where is ruthenium found?
Ruthenium is one of the platinum metals and occurs together with them. It is obtained as a by-product of refining platinum and of nickel mining.
What is ruthenium used for?
A little ruthenium makes platinum and palladium much harder, and such alloys go into electrical contacts that must not wear out. Adding just 0.1% ruthenium makes titanium about a hundred times more resistant to corrosion. Ruthenium compounds are also versatile catalysts in chemistry.
Interesting facts
Ruthenium tetroxide is a poisonous compound that can explode.