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.


Rhenium, symbol Re, rare, silvery white, metallic element. The atomic number of rhenium is 75. Rhenium is one of the transition elements of the periodic table.

The existence of rhenium and the similarity of its chemical properties to those of the element manganese were predicted in 1871 by the Russian chemist Dmitry Ivanovich Mendeleyev, who named it dvi-manganese. Rhenium was discovered in 1925 by the German chemists Walter Karl Noddack and Ida Eva Tacke Noddack in the ores tantalite, wolframite, and columbite by means of X-ray spectrographic analysis, and it was later found in larger quantities in molybdenite.

Rhenium metal is very hard; with the exception of tungsten, it is the least fusible of all common metals. Overall, it ranks about 79th in natural abundance among elements in crustal rocks. Rhenium melts at about 3180° C (about 5756° F), and has a specific gravity of 20.53. The atomic weight of rhenuim is 186.207.

Rhenium is used in electrical filaments, welding rods, thermocouples, cryogenic magnets, and photographic flashbulb filaments; it is also used as a catalyst.