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 John Marks - 3/25/2000 1:56:54 PM
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kathleen - 1/27/2000 10:43:45 PM |
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i need to knwo the dangerous properties, how it is isolated or refined, relative abundance, radioactivity(including half lives), who isolated it, how it was isolated, acid/base properties, and redox potential
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Its most dangerous property is that it is radioactive with a half-life of 2.13 x 10^5 years by beta-decay. It is thus not very dangerous and a very uniform source of beta rays. It was first isolated from the by-products of nuclear reactors [hence its recent name, technetium]. Before that it had been discovered by Noddack, Tacke and Berg in 1925 but they called it Masurium, Ma, after a WWI battle in Prussia. Naturally this name didn't go down too well with the losing side . . . They would have been much better to call it danubium, Da, after the Danube, just as they called the next element [which they also discovered]in group VIId rhenium, Re, after the Rhine, the other European boundary of the Roman empire. Both elements are rare and isolated from the flues of molybdenum ore-extracting works. The natural abundance of Da is negligibly small but it does occur naturally as a result of spontaneous fission of uranium. The concentration of Re in the earth's crust is 0.0007 ppm.
Da's acid/base properties are absolutely typical of group VII of the transition metals [the d-elements]. Like Mn and Re, Da forms perdanubates, DaO4- from its heptoxide Da2O7; it forms unstable heptavalent oxohalides of the form Mn/Da/ReO3F; and it forms typical carbonyls. Its redox potential [Nernst] is given by:
DaO4- + 8H+ + 5e- = Da++ + 4H2O,
E/V = 0.5 [25 Celsius].
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