Rhenium is a chemical element with symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. Discovered in 1925, rhenium was the last stable element to be discovered. It was named after the river Rhine in Europe. The picture shows the Deutsches Eck ("German Corner"), which is the name of a headland in Koblenz where the Moselle joins the Rhine.

With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust. The free element has the third-highest melting point and highest boiling point of any element. Rhenium resembles manganese and technetium chemically and is obtained as a by-product of molybdenum and copper ore's extraction and refinement. Rhenium shows in its compounds a wide variety of oxidation states ranging from −1 to +7.

Nickel-based superalloys of rhenium are used in the combustion chambers, turbine blades, and exhaust nozzles of jet engines. These alloys contain up to 6% rhenium, making jet engine construction the largest single use for the element, with the chemical industry's catalytic uses being next-most important. Because of the low availability relative to demand, rhenium is among the most expensive of metals, with an average price of approximately US$4,575 per kilogram (US$142.30 per troy ounce) as of August 2011; it is also of critical strategic military importance, for its use in high performance military jet and rocket engines.

History

Rhenium (Latin: Rhenus meaning: "Rhine") was the last-discovered of the elements that have a stable isotope (other new elements discovered in nature since then, such as neptunium and plutonium, are radioactive).The existence of a yet undiscovered element at this position in the periodic table had been first predicted by Dmitry Mendeleev. Other calculated information was obtained by Henry Moseley in 1914. It is generally considered to have been discovered by Walter Noddack, Ida Tacke, and Otto Berg in Germany. In 1925 they reported that they detected the element in platinum ore and in the mineral columbite. They also found rhenium in gadolinite and molybdenite.In 1928 they were able to extract 1 g of the element by processing 660 kg of molybdenite. It was estimated in 1968 that 75% of the rhenium metal in the United States was used for research and the development of refractory metal alloys. It took several years from that point on before the super alloys became widely used.

In 1908, Japanese chemist Masataka Ogawa announced that he discovered the 43rd element and named it nipponium (Np) after Japan (Nippon in Japanese). However, later analysis indicated the presence of rhenium (element 75), not element 43. The symbol Np was later used for the element neptunium.

Characteristics

Rhenium is a silvery-white metal with one of the highest melting points of all elements, exceeded by only tungsten and carbon. It also has the highest boiling point of all elements. It is also one of the densest, exceeded only by platinum, iridium and osmium. Rhenium has a hexagonal close-packed crystal structure, with lattice parameters a = 276.1 pm and c = 445.6 pm.

Its usual commercial form is a powder, but this element can be consolidated by pressing and sintering in a vacuum or hydrogen atmosphere. This procedure yields a compact solid having a density above 90% of the density of the metal. When annealed this metal is very ductile and can be bent, coiled, or rolled. Rhenium-molybdenum alloys are superconductive at 10 K; tungsten-rhenium alloys are also superconductive around 4–8 K, depending on the alloy

Rhenium is among the rarest metals on Earth. It does not occur uncombined in nature or as a compound in a mineable mineral species. It is, however, widely spread throughout the Earth’s crust to the extent of about 0.001 parts per million. Commercial production of rhenium is by extraction from the flue dusts of molybdenum smelters.

It is useful as an alloy to other refractory metals, where it adds ductility and tensile strength. Rhenium finds its most important use as a catalyst. It is used as a catalyst in reactions such as alkylation, dealkylation, hydrogenation and oxidation. However its rarity makes it the most expensive of the refractory metals

Health

The known uses for Rhenium include treatment of metastatic bone cancer, non-resectable liver cancer, non-melanoma skin cancer, treatment of arthritis and for inhibition of arterial restenosis following balloon angioplasty.

Metaphysical

Unknown