Technetium is a chemical element with the symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive. All available technetium is produced as a synthetic element. 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 both adjacent elements. The most common naturally occurring isotope is 99Tc, in traces only.

Many of technetium's properties had been predicted by Dmitri Mendeleev before it 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, technetos, from techne, as in "craft", "art" and having the meaning of "artificial", + -ium).

One short-lived gamma ray-emitting nuclear isomer, technetium-99m, is used in nuclear medicine for a wide variety of tests, such as bone cancer diagnoses. The ground state of the nuclide technetium-99 is used as a gamma-ray-free source of beta particles. Long-lived technetium isotopes produced commercially are byproducts of the fission of uranium-235 in nuclear reactors and are extracted from nuclear fuel rods. Because even the longest-lived isotope of technetium has a relatively short half-life (4. 21 million years), the 1952 detection of technetium in red giants helped to prove that stars can produce heavier elements.

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Atomic properties

Atomic mass(98.9063 u)

Atomic radii

Radius (empirical)136 pm
Radius (calculated)183 pm
Covalent radius147 ±7 pm
Van der Waals radius205 pm

Atomic shell

Electron configurationKr 4d5 5s2
Ionization energy(1st) 7.11938 eV
(2nd) 15.26 eV
(3rd) 29.55 eV
(4th) 41 eV
(5th) 57 eV
Shell model

Physical properties

Density11.5 g·cm−3 (298.1 K)
Molar volume8.63·10-6 m3·mol−1


Melting point2,430 K
Boiling point4,538 K
Liquid range2,108 K
Transition temperature8.2 K


Melting enthalpy23 kJ·mol-1
Enthalpy of vaporization550 kJ·mol-1
Binding energy661 kJ·mol-1

Heat and conductivity

Thermal conductivity51 W·m-1·K-1

Electrical properties

Electrical conductivity4.54·106 S·m-1
Resistance2.2·10-7 Ωm


Magnetic susceptibility2.7·10-4 cm3·mol−1 (298 K)

Chemical properties

Basicitystrongly acidic
Oxidation state-3 … 7
Standard potential0.272 V (TcO2 + 4e- + 4H+ → Tc + 2H2O)


Pauling scale1.9
Allred-Rochow scale1.36
Ghosh-Gupta scale3.224 eV
Nagle scale1.3

Other properties

Natural occurrenceDecay product
Crystal structureHexagonal close-packed
Goldschmidt Classificationsynthetic
Superconductorwith transition tempperature (solid body, normal pressure)
Radioactivityslightly radioactive
Price/kg100,000 USD