Technetium (43)

Since its discovery, searches for the element technetium [TEK-NET-EE-UM] in terrestrial materials have been made without success. 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-grey metal that tarnishes slowly in moist air. Until 1960, technetium was available only in small amounts. The chemistry of technetium is related to that of rhenium.

•Name: Technetium
•Symbol: Tc
•Atomic number: 43
•Atomic weight: [ 98 ]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-26-8
•Group in periodic table: 7
•Period in periodic table: 5
•Block in periodic table: d-block
•Color: silvery grey metallic
•Classification: Metallic

Historical information

Technetium was discovered by Carlo Perrier, Emilio Segre at 1937 in Italy. Origin of name is from the Greek word "technikos" meaning "artificial". Element 43 (technetium) was predicted on the basis of the periodic table by Mendeleev. He suggested that it should be very similar to manganese and gave it the name ekamanganese. Technetium was erroneously reported as having been discovered in 1925, at which time it was named masurium. The element was actually discovered by C. Perrier and Emilio Gino Segre in Italy in 1937. It was found in a sample of molybdenum bombarded by deuterons. Technetium was the first element to be produced artificially and all its isotopes are radioactive. It is named after the Greek technetos, artificial.

Physical properties

•Melting point: 2430 [or 2157 °C (3915 °F)] K
•Boiling point: 4538 [or 4265 °C (7709 °F)] K
•Density of solid: 11500 kg m-3

Orbital properties

•Ground state electron configuration: [Kr].4d6.5s1
•Shell structure: 2.8.18.14.1
•Term symbol: 6S5/2

Isolation

It is never necessary to make a sample of technetium anywhere other than specialist laboratories. This is because technetium is radioactive. Technetium is a byproduct of the nuclear industry and is a product of uranium decay. Alternatively it can be made by the bombardment of molydenum targets with deuterium nuclei.

Because of the scale of the nuclear industry it is possible to make quite large quantities of technetium (kilograms). The metal itself may be made by the reaction of the sulfide Tc2S7 with hydrogen at 1100°C or of the pertechnate NH4TcO4 with hydrogen.