What color does uranium burn
uranium, Symbol U, radioactive chem. Element from III. Subgroup of the periodic table, heavy metal belonging to the group of actinides; Z 92, atomic mass 238.029, valence mostly VI, IV, more rarely V, III, D. 18.97 g cm-3, M.p. 1132 ° C, b.p. 3900 ° C, standard electrode potential (U / U3+) -1.789 BC
Properties. U. is a silver-white, glossy, relatively soft, high-density metal that tends to tarnish rapidly in air and has three modifications - rhombic, tetragonal, body-centered cubic, transformation temperatures of 667 ° C and 772 ° C, respectively. Finely distributed, gray to black looking U. is very reactive and pyrophoric. U. is attacked by boiling water with evolution of hydrogen: U + 2 H2O → UO2 + 2 H.2; Even dilute acids react with U. with the evolution of hydrogen and the formation of uranium (IV) salts, while alkaline solutions do not attack U. Hydrogen reacts with U. at 250 to 300 ° C to form uranium hydride UH3 which is an important intermediate product in the synthesis of other uranium compounds and whose thermal decomposition at higher temperatures leads to particularly reactive U. With nitrogen, U. forms uranium nitrides, UN and U above 450 ° C2N3, around. Even if only moderately heated in the air, U. burns with sparks to form uranium (IV, VI) oxide U.3O8. The effect of halogen on U. leads to uranium halides, e.g. B. UF4 and UF6 UCl5 and UCl4, UBr4 and UI3.
U. and its compounds are highly toxic. All naturally occurring uranium isotopes are radioactive. The predominant isotope 238U (α; 4.51Â · 109 a) is the initial link of the uranium-radium decay series and passes over 234Th 234Pa and 234U and a number of other intermediates into the stable lead nuclide 208Pb (uranium lead) over (radioactivity). 235U forms the initial link of the uranium-actinium decay series, which is an α-emitter above 231Th and a number of other intermediates, finally, the stable lead nuclide 207Pb gives (radioactivity). 235U is different from 238U fissionable by slow neutrons. 238U forms with neutrons according to
Plutonium 239, a sequence of reactions that is used in breeder reactors to generate plutonium.
Analytical. In the classic cation separation process, U. appears in the urotroping group as ammonium diuranate (NH4)2U2O7, which in the gravimetric determination of uranium to U3O8 is burned up. Characteristic detection reactions are the very sensitive precipitation of brown uranyl hexacyanoferrate (II) (RO2)2[Fe (CN)6] with potassium hexacyanoferrate (II) or the formation of orange-yellow peroxouranate M4[UO2(O2)3] in alkaline solution. The formation of thiocyanate complexes is used for the spectrophotometric determination. With the help of the measurement of the fluorescent light traces up to about 10-10 PDO prove.
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