Technetium - chemistry.

Technetium - chemistry. Technetium, symbol Tc, radioactive metallic element, the first element to be created artificially. The atomic number of technetium is 43. Technetium is one of the transition elements of the periodic table (see Periodic Law). Technetium has no stable isotopes and is not part of the decay series of any naturally radioactive element (see Radioactivity). For these reasons scientists at first thought that technetium does not occur on Earth. In 1937 Emilio Segrè and Carlo Perrier created technetium by bombarding molybdenum targets with deuterons (particles consisting of a proton and a neutron). Minute quantities of the element have since been detected in uranium ores. The German chemists Walter Karl Noddack, Ida Eva Tacke Noddack, and Otto Berg may have detected this naturally-occurring technetium in 1925; they called it masurium. Technetium has also been detected spectroscopically in stars. Many isotopes of technetium are now known. The isotope with the longest half-life, 4.2 million years, has a mass number of 98. Technetium forms oxides, sulfides, and technetiates, such as ammonium technetiate (NH4TcO4). Compounds and alloys containing technetium oxide can prevent the corrosion of iron by water. Technetium-99 is used for imaging in medicine. Technetium melts at about 2157°C (about 3915°F), boils at about 4265°C (about 7709°F), and has a specific gravity of about 11.5. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.