Editing Period 5 element (section)

===Technetium===
{{main|Technetium}}

'''Technetium''' is the [[chemical element]] with [[atomic number]] 43 and symbol '''Tc'''. It is the lowest [[atomic number]] element without any [[stable isotope]]s; every form of it is [[radioactive]]. Nearly all technetium is produced synthetically and only minute amounts are found in nature. Naturally occurring technetium occurs as a spontaneous [[fission product]] in [[uranium ore]] or by [[neutron capture]] in [[molybdenum]] ores. The chemical properties of this silvery gray, crystalline [[transition metal]] are intermediate between [[rhenium]] and [[manganese]].

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 ''[[Mendeleev's predicted elements|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 language|Greek]] {{lang|el|τεχνητός}}, meaning "artificial").

Its short-lived [[gamma ray]]-emitting [[nuclear isomer]]—[[technetium-99m]]—is used in [[nuclear medicine]] for a wide variety of diagnostic tests. Technetium-99 is used as a gamma ray-free source of [[beta particle]]s. Long-lived [[isotopes of technetium|technetium isotopes]] produced commercially are by-products of [[nuclear fission|fission]] of [[uranium-235]] in [[nuclear reactor]]s and are extracted from [[nuclear fuel cycle|nuclear fuel rods]]. Because no isotope of technetium has a [[half-life]] longer than 4.2&nbsp;million years ([[technetium-98]]), its detection in [[red giant]]s in 1952, which are billions of years old, helped bolster the theory that stars can produce heavier elements.