Matter & Energy

Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.


Ruthenium, symbol Ru, chemically unreactive, grayish-white metallic element. Ruthenium is one of the transition elements of the periodic table. The atomic number of ruthenium is 44.

Ruthenium was discovered in 1844 by the Russian chemist Karl Karlovich Klaus. The name of the element is derived from the region of Ruthenia, now a part of Ukraine. The metal occurs in the metallic state in platinum ores. Ruthenium ranks 80th in natural abundance among elements in crustal rocks. Ruthenium melts at about 2310° C (about 4190° F), boils at about 3900° C (about 7052° F), and has a specific gravity of 12.3. The atomic weight of ruthenium is 101.07.

The addition of ruthenium to platinum and palladium alloys makes the alloys very hard. Such alloys have a high resistance to wear and are used in the manufacture of jewelry, in porcelain-metal restorations in dentistry, as tips for fountain-pen nibs, and for nonmagnetic instrument pivots. The alloy ruthenium-molybdenum is a superconductor at temperatures below -263° C (-441.4° F) (see Superconductivity). The pure metal is superior to platinum in resistance to attack by acids, including aqua regia.