On the periodic table, technetium was the first element synthesized artificially and was discovered in 1937.
Technetium has atomic number 43. Emilio Segrè and Carlo Perrier identified it in molybdenum foil that had been exposed to the deuterons of a cyclotron. The name technetium comes from the Greek technetos, meaning artificial, reflecting its history.
Technetium was notable because the periodic table predicted an element between molybdenum and ruthenium, yet no stable natural sample had been found. All technetium isotopes are radioactive, although tiny natural quantities can form in uranium ores. Technetium-99m is especially important in nuclear medicine, where its short-lived gamma emissions help create diagnostic images. It should not be confused with promethium, another radioactive element with no stable isotopes.