Rhenium

When Russian chemist Dmitri Mendeleev rolled out his groundbreaking periodic table of the elements in 1869, element 25—manganese—was the only element with two gaps below it, leaving room for elements that Mendeleev predicted would exist. One of those elements was eventually found to be element 43, technetium. The other was element 75, which would come to be known as rhenium.

In 1908, Japanese chemist Masataka Ogawa claimed to have found element 43, which he called nipponium, after one of the Japanese words for Japan. But no one was able to replicate his work and his claim was rejected. Later, another Japanese chemist, Kenjiro Kimura, figured out why Ogawa’s work had never been replicated; Ogawa had actually discovered element 75! Because the elements are in the same group, they are a lot alike—so Ogawa had good reason to be confused!

German chemists Walter Noddack, Ida Tacke, and Otto Berg rediscovered the element in 1925, extracting it from platinum ore and columbite. Rhenium was exceedingly hard to isolate; the team had to process 660 kilograms of the mineral molybdenite to get 1 gram of rhenium! Rhenium is one of the rarest elements there is!

The Noddack team named the new element “rhenium” after the Latin word Rhenus, for the Rhine River—an important waterway in Germany.

Rhenium has the third-highest melting point (and the second-highest boiling point) of any element. When it isn’t molten, rhenium is a silver metal that’s often sold as a powder. 

Most rhenium—up to 80%—is alloyed with the metals that make up turbine blades for airplane and industrial turbine engines. That’s because rhenium has one of the highest melting points of all metals. With a melting point of nearly 3200°C, rhenium can withstand a lot of heat!

Other uses for rhenium include fossil-fuel refining and, experimentally, in cancer treatments.

The rhenium compound (Re₂Cl₈)₂ is important in the history of chemistry. This rhenium compound showed that it was possible in nature for two atoms to have a quadruple bond. Good luck trying to pry those atoms apart!

Rhenium forms in lots of oxidation states. Rhenium dioxide is often used as a catalyst. Rhenium(VII) oxide is an important compound, serving as the basis of all rhenium compounds.

Commercially, you’ll often find rhenium in the form of perrhenate salts.

In nature, rhenium has just one stable isotope, rhenium-185. A little less than 40% of rhenium is found in this form, while the rest is rhenium-187—a radioactive isotope of the element with a very long half-life (4.16×10¹⁰ years). That’s a lot of zeroes!

Scientists have created around 30 radioactive rhenium isotopes.

Most rhenium comes from copper-porphyry ores. Both molybdenum and rhenium are produced as byproducts from processing these ores.

Chile is the biggest producer of rhenium, followed by the United States and Poland.