Meitnerium

Meitnerium is a purely synthetic element. It does not exist in nature. Like other synthetic elements, it is highly radioactive and decays in seconds or fractions of a second.

The first meitnerium atom was created in 1982 at the Heavy Ion Research Laboratory in Darmstadt, Germany (then West Germany). A team lead by German physicists Peter Armbruster and Gottfried Münzenberg bombarded a target of bismuth-209 with accelerated iron-58 nuclei. This caused the two different nuclei to undergo fusion, merging into meitnerium-266. Then, 5 milliseconds after it appeared, it decayed!

Armbruster and Münzenberg recommended that the new element be named after Lise Meitner, an Austrian physicist who coined the term "nuclear fission." Working with colleagues in 1938, she found that bombarding thorium with neutrons caused the thorium to split into lighter elements. The following year, she and her nephew, physicist Otto Robert Frisch, figured out how the splitting occurs and published their findings. They named the process “fission.” Soon thereafter, the Experimental Breeder Reactor-1 (a collaboration between what is now Argonne National Laboratory and Idaho National Laboratory) generated the first usable electricity from atomic fission. Now, nuclear power is the nation's largest source of next-generation energy, providing high-efficiency electricity to modernize the nation’s energy infrastructure.

Very few meitnerium atoms have ever been made. Because they’re made one atom at a time and decay rapidly, it’s not possible to measure the element's basic properties, like density and boiling point. Even the atomic mass is unknown. Like other synthetic elements, its mass number is simply assigned from its longest-lived isotope, meitnerium-287. It is expected to have similar properties to the metals directly above it on the periodic table (cobalt, rhodium, and iridium). It should be solid at room temperature, but none of this can be confirmed!

Meitnerium has no uses beyond fundamental physics research. 

Meitnerium is a synthetic element and can only be produced in a laboratory. It decays almost immediately after it forms.