Editing Period 6 element (section)

===Rhenium===
{{main|Rhenium}}
'''Rhenium''' is a [[chemical element]] with the symbol '''Re''' and [[atomic number]] 75. It is a silvery-white, heavy, third-row [[transition metal]] in [[group 7 element|group 7]] of the [[periodic table]]. With an ''estimated'' average concentration of 1 [[Parts-per notation|part per billion]] (ppb), rhenium is one of the rarest elements in the [[Earth's crust]]. The free element has the [[List of elements by melting point|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 [[copper]] ore's extraction and refinement. Rhenium shows in its compounds a wide variety of [[oxidation state]]s 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]] of rhenium are used in the combustion chambers, turbine blades, and exhaust nozzles of [[jet engine]]s, 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.<ref>{{cite web |url=http://www.metalprices.com/FreeSite/metals/re/re.asp |title=Rhenium |work=MetalPrices.com |access-date=February 2, 2012 |archive-date=January 15, 2012 |archive-url=https://web.archive.org/web/20120115004912/http://www.metalprices.com/FreeSite/metals/re/re.asp |url-status=dead }}</ref>