Description
تفصیل
is the chemical element with atomic number 43 and symbol Tc. It is the lowest atomic number element without any stable isotopes; every form of it is radioactive. Nearly all technetium is produced synthetically and only minute amounts are found in nature. Naturally occurring technetium occurs as a spontaneous fission product in uranium ore or by neutron capture in molybdenum ores. The chemical properties of this silvery gray, crystalline transition metal are intermediate between rhenium and manganese.
From the 1860s through 1871, early forms of the periodic table proposed by Dimitri Mendeleev contained a gap between molybdenum (element 42) and ruthenium (element 44). In 1871, Mendeleev predicted this missing element would occupy the empty place below manganese and therefore have similar chemical properties. Mendeleev gave it the provisional name ekamanganese (eka- from the Sanskrit words for one), because the predicted element was one place down from the known element manganese.
The discovery of element 43 was finally confirmed in a December 1936 experiment at the University of Palermo in Sicily conducted by Carlo Perrier and Emilio Segrè.
References
Technetium: technetium(III) iodide compound data". OpenMOPAC.net. Retrieved 2007-12-10.
Technetium: technetium(I) fluoride compound data". OpenMOPAC.net. Retrieved 2007-12-10.
Jonge, F. A. A.; Pauwels, EK (1996). "Technetium, the missing element". European Journal of Nuclear Medicine 23 (3): 336–44. doi:10.1007/BF00837634. PMID 8599967.
a b Holden, N. E.. "History of the Origin of the Chemical Elements and Their Discoverers". Brookhaven National Laboratory. Retrieved 2009-05-05.
