Appearance and Characteristics
Harmful effects:
Technetium is harmful due to its radioactivity.
Characteristics:
Technetium is a rare, silver-gray metal that tarnishes slowly in moist air.
In powder form, it burns in oxygen to the heptoxide (Tc2O7).
Technetium dissolves in nitric acid and concentrated sulfuric acid, but is not soluble in hydrochloric acid of any strength.
Is an excellent superconductor at temperatures of 11 K and below.
Technetium and promethium are unusual among the light elements, because they have no stable isotopes.
Uses of Technetium
Technetium-99m is a metastable isotope with a half-life of six hours. Technetium-99m emits gamma rays and low energy electrons, forming technetium-99 (half-life 211 000 years). The gamma rays can be photographed using a gamma camera, and technetium-99m is used in 80 to 90 percent of all diagnostic procedures that use radioactive elements.
Technetium-95, with a half-life of 61 days, is used as a radioactive tracer.
Technetium-99, has a very long half-life (2.11 X 105 years) and decays almost entirely by beta decay with no gamma rays. It is used as for equipment calibration.
In small concentrations the pertechnetate ion (TcO 4-) can protect carbon steels and iron from corrosion. This use is limited to closed systems due to its radioactivity.