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Protactinium-231 is the longest-lived isotope of protactinium, with a half-life of 32,760 years. In nature, it is found in trace amounts as part of the actinium series, which starts with the primordial isotope uranium-235; the equilibrium concentration in uranium ore is 46.55 231 Pa per million 235 U.
Pages in category "Isotopes of protactinium" ... Protactinium-235; Protactinium-236; Protactinium-237; Protactinium-238; Protactinium-239; Protactinium-240 ...
The longest-lived and most abundant (nearly 100%) naturally occurring isotope of protactinium, protactinium-231, has a half-life of 32,760 years and is a decay product of uranium-235. Much smaller trace amounts of the short-lived protactinium-234 and its nuclear isomer protactinium-234m occur in the decay chain of uranium-238 .
Protactinyl nitrate, protactinium(V) oxynitrate, or erroneously known as protactinium nitrate, is a radioactive chemical compound with the formula PaO(NO 3) 3 ·xH 2 O (1.5 ≤ x ≤ 4). It is a white solid that readily hydrolyzes to protactinium(V) oxide in moist air. This compound is a common commercial source of protactinium. [2]
Protactinium(V) bromide has two similar monoclinic forms, one is obtained by sublimation at 400–410 °C and another by sublimation at slightly lower temperature of 390–400 °C. [5] [7] Protactinium iodides result from the oxides and aluminium iodide or ammonium iodide heated to 600 °C. [2]
The largest component is the remaining uranium which is around 98.25% uranium-238, 1.1% uranium-235, and 0.65% uranium-236. The U-236 comes from the non-fission capture reaction where U-235 absorbs a neutron but releases only a high energy gamma ray instead of undergoing fission.
Initially only about 0.7% of it is fissile U-235, with the rest being almost entirely uranium-238 (U-238). They are separated by their differing masses. Highly enriched uranium is considered weapons-grade when it has been enriched to about 90% U-235. [citation needed] U-233 is produced from thorium-232 by neutron capture. [19]
Protactinium(V) bromide is an orange-red, crystalline, extremely moisture-sensitive solid that reacts violently with water and ammonia, but is persistent in absolutely dry air. It is insoluble in isopentane, dichloromethane and benzene, and in anhydrous acetonitrile is dissolves to form PaBr 5 •4CH 3 CN. It comes in several modifications.