technetium

Silver-grey, radioactive, metallic element, atomic number 43, relative atomic mass 98.906. It occurs in nature only in extremely minute amounts, produced as a fission product from uranium in pitchblende and other uranium ores. Its longest-lived isotope, Tc-99, has a half-life of 216,000 years. It is a superconductor and is used as a hardener in steel alloys and as a medical tracer.

It was synthesized in 1937 (named in 1947) by Italian physicists Carlo Perrier and Emilio Segrè, who bombarded molybdenum with deuterons, looking to fill a gap in the periodic table of the elements (at that time it was considered not to occur in nature). It was later isolated in larger amounts from the fission product debris of uranium fuel in nuclear reactors.