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Ruthenium                                                                                                                                    

Standard Sate: solid at 298 K

Color:  silvery white metallic

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.

(Ru), chemical element, one of the platinum metals of Group VIII of
the periodic table, used as an alloying agent to harden platinum and
palladium. Silver-gray ruthenium metal looks like platinum but is
rarer, harder, and more brittle. The Russian chemist Karl Karlovich
Klaus established (1844) the existence of this rare metal and retained
the name his countryman Gottfried Wilhelm Osann had suggested
(1828) for a platinum-group element whose discovery had remained
inconclusive. Elemental ruthenium occurs in native alloys of iridium
and osmium: up to 14.1 percent in iridosmine and 18.3 percent in
siserskite. It also occurs in sulfide and other ores (e.g., in pentlandite
of the Sudbury, Ont., Can., nickel-mining region) in very small
quantities that are commercially recovered.

Because of its high melting point, ruthenium is not easily cast; its
brittleness, even at white heat, makes it very difficult to roll or draw
into wires. Thus, the industrial application of metallic ruthenium is
restricted to use as an alloy for platinum and other metals of the
platinum group. It serves the same function as iridium for the
hardening of platinum and, in conjunction with rhodium, is used to
harden palladium. Ruthenium-hardened alloys of platinum and
palladium are superior to the pure metals in the manufacture of fine
jewelry and of electrical contacts for wear resistance.

Ruthenium is found among the fission products of uranium and
plutonium in nuclear reactors. Radioactive ruthenium-106 (one-year
half-life) and its short-lived daughter rhodium-106 contribute an
important fraction of the residual radiation in reactor fuels a year
following their use. Recovery of the unused fissionable material is
made difficult because of the radiation hazard and the chemical
similarity between ruthenium and plutonium.

Natural ruthenium consists of a mixture of seven stable isotopes:
ruthenium-96 (5.54 percent), ruthenium-98 (1.86 percent),
ruthenium-99 (12.7 percent), ruthenium-100 (12.6 percent),
ruthenium-101 (17.1 percent), ruthenium-102 (31.6 percent), and
ruthenium-104 (18.6 percent). It has four allotropic forms. The
metal does not tarnish in air at ordinary temperatures and resists
attack by strong acids, even by aqua regia. Ruthenium is brought
into soluble form by fusion with an alkaline oxidizing flux, such as
sodium peroxide (Na2O2). The green melt contains the perruthenate
ion, RuO-4; on dissolving in water, an orange solution containing the
stable ruthenate ion, RuO42-, usually results. Very volatile ruthenium
tetroxide, RuO4, used in separating ruthenium from other heavy
metals, contains the element in the +8 oxidation state. All states from
zero through +8 are known, but +3, +4, +6, and +8 are most
important. Numerous coordination complexes are known, including a
unique series of nitrosyl (NO) complexes. atomic number 44 atomic
weight 101.07 melting point 2,250 C (4,082 F) boiling point 3,900 C
(7,052 F) specific gravity 12.30 (20 C) valence 1, 2, 3, 4, 5, 6, 7, 8
electronic config. 2-8-18-15-1 or (Kr)4d75s1

"ruthenium" Encyclop�dia Britannica Online.

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