Atomic Number:


Melting Point: 2157 C
Atomic Symbol: Tc Boiling Point:  4265 C
Atomic Weight: 97 amu Density: 856 kg/m 3
Atomic Radius:

135.8 pm

Oxidation States: 7, 6, 4
Covalent Radius: 196 pm Electron Configuration: [Kr]5s24d5
van der Waals Radius:

275 pm

State of Matter: solid 


(Gr. technetos: artificial) Element 43 was predicted on the basis of the periodic table, and was erroneously reported as having been discovered in 1925, at which time it was named masurium. The element was actually discovered by Perrier and Segre in Italy in 1937. It was also found in a sample of molybdenum sent by E. Lawrence that was bombarded by deuterons in the Berkeley cyclotron. Technetium was the first element to be produced artificially. Since its discovery, searches for the element in terrestrial material have been made.  Finally in 1962, technetium-99 was isolated and identified in African pitchblende (a uranium rich ore) in extremely minute quantities as a spontaneous fission product of uranium-238 by B.T. Kenna and P.K. Kuroda.  If it does exist, the concentration must be very small. Technetium has been found in the spectrum of S-, M-, and N-type stars, and its presence in stellar matter is leading to new theories of the production of heavy elements in the stars.


Technetium is a silvery-gray metal that tarnishes slowly in moist air.  The common oxidation states of technetium are +7, +5, and +4. Under oxidizing conditions technetium (VII) will exist as the pertechnetate ion, TcO4-.  The chemistry of technetium is said to be similar to that of rhenium. Technetium dissolves in nitric acid, aqua regia, and concentrated sulfuric acid, but is not soluble in hydrochloric acid of any strength.


Once it was available in macroscopic quantities i.e. enough to determine its chemical and physical properties, it was discovered to exist naturally elsewhere in the universe. Some red giant stars (S-, M-, and N-types) contain an emission line in their spectrum corresponding to the presence of technetium. Its presence in red giants has led to the establishment of new theories about the production of heavy elements in stars.

Since its discovery, there have been many searches in terrestrial materials for natural sources. In 1962, technetium-99 was isolated and identified in pitchblende from Africa in very small quantities as a spontaneous fission product of uranium-238. This discovery was made by B.T. Kenna and P.K. Kuroda.


Technetium is one of the most powerful known preventatives of rust, and is also a valuable source of beta rays. Ammonium pertechnate, is a specialized corrosion preventer for steel. Five parts per million of KTcO4 in aerated distilled water protects mild carbon steel at temperatures up to 250 C. This protection is limited to closed systems due to the radioactive nature of technetium. Organic technetium compounds are used in bone imaging. It is an excellent superconductor at tempuratures of 11 kelvins and below.


Twenty-two isotopes of technetium with masses ranging from 90 to 111 are reported. All the isotopes of technetium are radioactive. It is one of two elements with Z < 83 that have no stable isotopes; the other element is promethium (Z = 61). Technetium has three long lived radioactive isotopes: 97Tc (T1/2 =2.6 x 106 years), 98Tc (T1/2 = 4.2 x 106 years) and 99Tc (T1/2 = 2.1 x 105 years).   95Tcm ("m" stands for meta state) (T1/2 = 61 days) is used in tracer work. However, the most useful isotope of technetium is 99Tcm (T1/2 = 6.01 hours) is used in many medical radioactive isotope tests because of its half-life being short, the energy of the gamma ray it emits, and the ability of technetium to be chemically bound to many biologically active molecules. Because 99Tc is produced as a fission product from the fission of uranium in nuclear reactors, large quantities have been produced over the years. There are kilogram quantities of technetium currently existing.


It is reported that mild carbon steels may be effectively protected by as little as 55 ppm of KTcO4 in aerated distilled water at temperatures up to 250oC. This corrosion protection is limited to closed systems, since technetium is radioactive and must be confined. 98Tc has a specific activity of 6.2 x 108 Bq/g. Activity of this level must not be allowed to spread. 99Tc is a contamination hazard and should be handled in a glove box.