technetium is a chemical element with the symboltc and atomic number 43. it is the lightest element whose isotopes are all radioactive; none are stable other than the fully ionized state of 97tc. nearly all technetium is produced as a synthetic element, and only about 18,000 tons are estimated to exist at any given time in the earth's crust. naturally occurring technetium is a spontaneous fission product in uranium ore and thorium ore, the most common source, or the product of neutron capture in molybdenum ores. this silvery gray, crystalline transition metal lies between manganese and rhenium in group 7 of the periodic table, and its chemical properties are intermediate between those of these two adjacent elements. the most common naturally occurring isotope is 99tc.
many of technetium's properties were predicted by dmitri mendeleev before the element was discovered. mendeleev noted a gap in his periodic table and gave the undiscovered element the provisional name ekamanganese (em). in 1937, technetium (specifically the technetium-97 isotope) became the first predominantly artificial element to be produced, hence its name (from the greek τεχνητός, meaning "synthetic or artificial", + -ium).
one short-lived gamma ray-emitting nuclear isomer of technetium—technetium-99m—is used in nuclear medicine for a wide variety of diagnostic tests, such as bone cancer diagnoses. the ground state of this nuclide, technetium-99, is used as a gamma-ray-free source of beta particles. long-lived technetium isotopes produced commercially are by-products of the fission of uranium-235 in nuclear reactors and are extracted from nuclear fuel rods. because no isotope of technetium has a half-life longer than 4.21 million years (technetium-97), the 1952 detection of technetium in red giants helped to prove that stars can produce heavier elements.
Many of technetium's properties were predicted by Dmitri Mendeleev before the element was discovered. Mendeleev noted a gap in his periodic table and gave the undiscovered element the provisional name ekamanganese (Em). In 1937, technetium (specifically the technetium-97 isotope) became the first predominantly artificial element to be produced, hence its name (from the Greek τεχνητός, meaning "synthetic or artificial", + -ium).