Technetium (Tc)

Isotopes of Technetium

Isotope Atomic Mass Half-life Mode of Decay Nuclear Spin Nuclear Magnetic Moment
Tc-93  92.910248  2.73 hours  EC to Mo-93 9/2 6.26
Tc-94 93.909655 4.88 hours EC to Mo-94 7 5.08
Tc-95 94.90766 20.00 hours EC to Mo-95 9/2 5.89
Tc-96 95.90787 4.30 days EC to Mo-96 7 5.04
Tc-97 96.906364 2.60 x 106 years EC to Mo-97 9/2 No data available 
Tc-98 97.907215 4.20 x 106 years β- to Ru-98 6 No data available 
Tc-99  98.907  213,000 years  β- to Ru-99 9/2  5.6847


Technetium was discovered in 1936 by Carlo Perrier and Emilio Segrè. Its name comes from the Greek word technetos, meaning “artificial.” It is the lowest atomic number element without any stable isotopes; every form of technetium is radioactive.

Technetium is a silver-gray metal with a hexagonal close-packed crystal structure. Its chemical properties are intermediate between those of rhenium and manganese. Technetium dissolves in aqua regia, nitric acid and concentrated sulfuric acid, but it is not soluble in hydrochloric acid. The metal form is slightly paramagnetic, tarnishes slowly in moist air and, in powder form, will burn in oxygen.

Only minute traces of technetium occur naturally in the Earth's crust. Small amounts exist as spontaneous fission products in uranium ores. Some red giant stars are indicated to contain technetium — these are known informally as “technetium stars.” In contrast with its rare natural occurrence, bulk quantities of the isotope Technetium-99 are produced each year from spent nuclear fuel rods.

The metastable isotope Technetium-99m is used in nuclear medicine for a wide variety of diagnostic tests, including imaging and functional studies of the brain, myocardium, thyroid, lungs, liver, gallbladder, kidneys, skeleton, blood and tumors. Technetium-99 is a United States National Institute of Standards and Technology (NIST) standard beta emitter and is therefore used for equipment calibration. Technetium can be used as a catalyst, although its radioactivity limits the safety of these applications.

Properties of Technetium

Name Technetium 
Symbol Tc 
Atomic number 43 
Atomic weight 98 
Standard state Solid at 298 ºK 
CAS Registry ID 7440-26-8
Group in periodic table
Group name None 
Period in periodic table
Block in periodic table d-block 
Color Silvery gray metallic 
Classification Metallic 
Melting point 2157 °C
Boiling point 4265 °C
Thermal conductivity 50.6 W/(m·K)
Electronegativity 1.9 
Heat of vaporization 585.2 kJ·mol-1
Heat of fusion 33.29 kJ·mol-1
Density of solid 11 g/cm
Electron configuration [Kr]4d55s2 
Oxidation states  -3, -1, +1, +2, +3, +4, +5, +6, +7 

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