Rhenium

Rhenium is a chemical element with the atomic symbol **Re** and atomic number 75. It is a silvery-white, heavy, third-row transition metal in Group 7 of the periodic table. With an 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 chemically and is obtained as a by-product of molybdenum and refinement. Rhenium shows in its compounds a wide variety of oxidation states ranging from −1 to +7. Discovered in 1925, rhenium was the last stable element to be discovered. It was named after the river Rhine in Europe. Nickel-based superalloys for use in jet engines contain up to 6% rhenium, making jet engine construction the largest use for the element, with chemical industry catalytic uses being next-most important. Because of the low availability relative to demand, rhenium is among the most expensive metals, with an average price of approximately US$4,575 per kilogram.

Rhenium is one of the rarest elements in Earth's crust with an average concentration of 1 ppb;[19home] other sources quote the number of 0.5 ppb making it the 77th most abundant element in Earth's crust.[26home] Rhenium is probably not found free in nature (its possible natural occurrence is uncertain), but occurs in amounts up to 0.2%[19home] in the mineral molybdenite (which is primarily molybdenum disulfide), the major commercial source, although single molybdenite samples with up to 1.88% have been found.[27home] Chile has the world's largest rhenium reserves, part of the copper ore deposits, and was the leading producer as of 2005.[28home] It was only recently that the first rhenium mineral was found and described (in 1994), a rhenium sulfide mineral (ReS2) condensing from a fumarole on Russia's Kudriavy volcano, Iturup island, in the Kurile Islands.[29home] Kudryavy discharges up to 20–60 kg rhenium per year mostly in the form of rhenium disulfide.[30home][31home] Named rheniite, this rare mineral commands high prices among collectors.[32home]


 * Atomic Number:** 75
 * Atomic Weight:** 186.207
 * Melting Point:** 3459 K (3186°C or 5767°F)
 * Boiling Point:** 5869 K (5596°C or 10105°F)
 * Density:** 20.8 grams per cubic centimeter
 * Phase at Room Temperature:** Solid
 * Element Classification:** Metal
 * Period Number:** 6 **Group Number:** 7 **Group Name:** none

Rhenium was discovered by the German chemists Ida Tacke-Noddack, Walter Noddack and Otto Carl Berg in 1925. They detected rhenium spectroscopically in platinum ores and in the minerals columbite ((Fe, Mn, Mg)(Nb, Ta)2O6), gadolinite ((Ce, La, Nd, Y)2FeBe2Si2O10) and molybdenite (MoS2). Rhenium is present in these materials only in trace amounts. In 1928, Noddack and Berg were able to extract 1 gram of rhenium from 660 kilograms of molybdenite. Today, rhenium is obtained as a byproduct of refining molybdenum and copper. Rhenium is used in flash lamps for photography and for filaments in mass spectrographs and ion gages, but is most frequently used as an alloying agent in tungsten and molybdenum and as a catalyst for performing certain reactions to a type of hydrocarbon known as an olefin.
 * History and Uses:**
 * additive to tungsten and molybdenum-based alloys to impart useful properties
 * filaments for mass spectrographs and ion gauges
 * rhenium-molybdenum alloys superconduct at 10K
 * electrical contact material, as it has good wear resistance and withstands arc corrosion
 * thermocouples made of Re-W are used for measuring temperatures up to 2200°C
 * rhenium wire is used in flash lamps for photography
 * rhenium catalysts are exceptionally resistant to poisoning from nitrogen, sulphur, and phosphorus, and are used for hydrogenation of fine chemicals, hydrocracking, reforming, and the disproportionation of alkenes
 * Estimated Crustal Abundance:** 7×10-4 milligrams per kilogram
 * Estimated Oceanic Abundance:** 4×10-6 milligrams per liter
 * Number of Stable Isotopes:** 1
 * Ionization Energy:** 7.88 eV
 * Oxidation States:** +7, +6, +4

Discovery of Rhenium
Before rhenium was discovered, its existence was predicted by Henry Moseley in 1913, based on his experimental study of elements' atomic numbers.

The element name comes from Latin word 'Rhenus', meaning Rhine
 * Symbol:** Re **Atomic Number:** 75 **Atomic Mass:** 186.207 amu **Melting Point:** 3180.0 °C (3453.15 K, 5756.0 °F) **Boiling Point:** 5627.0 °C (5900.15 K, 10160.6 °F) **Number of Protons/Electrons:** 75 **Number of Neutrons:** 111 **Classification:** Transition Metal **Crystal Structure:** Hexagonal **Density @ 293 K:** 21.02 g/cm3 **Color:** silverish

Atomic Structure

 * [[image:http://www.chemicalelements.com/bohr/b0075.gif width="355" height="353"]] ||  || **Number of Energy Levels:** 6
 * First Energy Level:** **Second Energy Level:** **Third Energy Level:** **Fourth Energy Level:** **Fifth Energy Level:** **Sixth Energy Level:** ||

Isotopes

 * ** Isotope ** || ** Half Life ** ||
 * Re-182 || 2.67 days ||
 * Re-182m || 12.7 hours ||
 * Re-183 || 70.0 days ||
 * Re-184 || 38.0 days ||
 * Re-184m || 165.0 days ||
 * Re-185 || Stable ||
 * Re-186 || 3.77 days ||
 * Re-187 || 4.1E10 years ||
 * Re-188 || 16.94 hours ||

Facts

 * Date of Discovery:** 1925 **Discoverer:** Walter Noddack **Name Origin:** From Rhines provinces of Germany **Uses:** filaments for mass spectrographs **Obtained From:** gadolinite, molybdenite