Tc

Technetium, with the symbol Tc and atomic number 43, is a silvery-gray, radioactive transition metal. It is the lightest element with no stable isotopes and occurs only in trace amounts in nature. Technetium is mostly produced synthetically in nuclear reactors or particle accelerators, though trace quantities can arise from spontaneous fission of heavier elements. It was the first element to be artificially produced, identified in 1937 by Carlo Perrier and Emilio Segrè from irradiated molybdenum, and its name derives from the Greek technetos, meaning artificial.

The element has numerous radioactive isotopes, all unstable. The most widely used is technetium-99m, a metastable isomer with a half-life of about six hours, fundamental to modern diagnostic medicine. Technetium-99m is typically supplied to clinics from molybdenum-99/tc-99m generators, where the parent nuclide decays to the short-lived metastable state. Other technetium isotopes serve in research, industry, or as long-lived beta emitters in environmental studies; technetium-99, for example, has a much longer half-life and is a concern in nuclear waste management due to its mobility as the pertechnetate ion.

Chemically, technetium exhibits a variety of oxidation states from -1 to +7 and forms compounds such as oxides, halides, and oxoanions like pertechnetate (TcO4−). It tends to form volatile oxides and can participate in coordination chemistry similar to other transition metals.

Safety and regulation accompany its use, given its radioactivity and potential environmental mobility. Technetium remains a central element in nuclear medicine and radiochemical research.