Periodic Table


Atomic number: 44
Atomic weight: 101.07
Symbol: Ru
Group number: 8
Electronic configuration: [Kr].4d75s1


Ruthenium is a hard, white metal. It does not tarnish at room temperatures, but oxidises in air at about 800°C. The metal is not attacked by hot or cold acids or aqua regia, but when potassium chlorate is added to the solution, it oxidises explosively.

General information

Discoveror: Karl Karlovich Klaus
Date discovered: 1844
Discovered at: Russia
Meaning of name: From the Latin word "Ruthenia" meaning "Russia"

Physical data

Standard state: solid at 298 K
Colour: silvery white metallic
Density of solid at ambient temperature/kg m-3: 12370
Molar volume/cm3: 8.17

Radii /pm

Atomic: 178
Covalent (single bond):
Pauling radius for the ion [Ru]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius164.7no data63.9no data


Both values are quoted on the Pauling scale.

Pauling: 2.2
Allred Rochow: 1.42

Crystal Structure

structure: hcp (hexagonal close-packed)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.


Temperatures (/K)

melting point: 2607
boiling point: 4423

Enthalpies /kJ mol-1

fusion: 25.9
vaporization: 579

single bond enthalpies:
Ru-F Ru-Cl Ru-Br Ru-I Ru-Ru
no data no data no data no data no data

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
96Ru95.907599 (8)5.52 (6)
98Ru97.905287 (7)1.88 (8)
99Ru98.9059389 (23)12.7 (1)
100Ru99.9042192 (24)12.6 (1)
101Ru100.9055819 (24)17.0 (1)
102Ru101.9043485 (25)31.6 (2)
104Ru103.905424 (6)18.7 (2)

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/Ru.html