technetium

Technetium is a chemical element with the symbol Tc and atomic number 43. It is a transition metal, belonging to group 7, and is notable for having no stable isotopes; all of its isotopes are radioactive. Technetium was discovered in 1937 by Carlo Perrier and Emilio Segrè in cyclotron experiments, and its name derives from the Greek technetos, meaning artificial.

Natural technetium is extremely scarce on Earth. Trace amounts occur from the spontaneous fission of heavier elements, but most technetium is produced synthetically in nuclear reactors or particle accelerators. A major practical application arises from technetium-99m, a metastable isomer that is widely used in medical diagnostic imaging because it emits gamma rays of about 140 keV and has a convenient half-life of roughly six hours. In clinical settings, technetium-99m is generated from a molybdenum-99 source via a technetium-99m generator, enabling on-site preparation of Tc-99m radiopharmaceuticals.

Isotopes and chemistry: Technetium has many radioisotopes; Tc-99 and Tc-99m are among the most important industrial and medical isotopes. Tc-99 has a long half-life, while Tc-99m dominates diagnostic imaging. Chemically, technetium exhibits multiple oxidation states, with +7 being common in soluble compounds such as the pertechnetate ion TcO4−, and it forms a variety of oxides and coordination compounds.

Safety: Technetium is radioactive, and handling requires appropriate shielding, monitoring, and regulatory controls.