Technetium is a chemical element with the symbol Tc and atomic number 43. It is unique in that all of its isotopes are radioactive, with varying half-lives ranging from a few milliseconds to several million years. This characteristic makes technetium essential in many medical procedures, such as diagnostic imaging and cancer treatments. Technetium was the first element to be produced artificially, first by Italian scientist Emilio Segrè in 1937, leading to the production of other synthetic elements. Despite being the 43rd element in the periodic table, technetium is one of the rarest naturally occurring elements on Earth due to its radioactive nature and short half-lives.