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Protactinium-231 arises naturally from the decay of natural uranium-235, and artificially in nuclear reactors by the reaction 232 Th + n → 231 Th + 2n and the subsequent beta decay of 231 Th. It was once thought to be able to support a nuclear chain reaction, which could in principle be used to build nuclear weapons ; the physicist Walter ...
However, the 231 Pa (with a half-life of 3.27 × 10 4 years) formed via (n,2n) reactions with 232 Th (yielding 231 Th that decays to 231 Pa), while not a transuranic waste, is a major contributor to the long-term radiotoxicity of spent nuclear fuel. While 231 Pa can in principle be converted back to 232
The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured.
All of the remaining radioactive isotopes have half-lives less than 1.6 days, and the majority of these have half-lives less than 1.8 seconds. This element also has five meta states, 217m Pa (t 1/2 1.15 milliseconds), 220m1 Pa (t 1/2 = 308 nanoseconds), 220m2 Pa (t 1/2 = 69 nanoseconds), 229m Pa (t 1/2 = 420 nanoseconds), and 234m Pa (t 1/2 = 1 ...
Aluminium's is 75.2 GPa; copper's 137.8 GPa; and mild steel's is 160–169 GPa. [12] Thorium is about as hard as soft steel, so when heated it can be rolled into sheets and pulled into wire. [13] Thorium is nearly half as dense as uranium and plutonium and is harder than both. [13] It becomes superconductive below 1.4 K. [11]
There are 39 known isotopes of radon (86 Rn), from 193 Rn to 231 Rn; all are radioactive.The most stable isotope is 222 Rn with a half-life of 3.8235 days, which decays into 218 Po
One isotope, 229 Th, has a nuclear isomer (or metastable state) with a remarkably low excitation energy, [5] recently measured to be 8.355 733 554 021 (8) eV [6] [7] It has been proposed to perform laser spectroscopy of the 229 Th nucleus and use the low-energy transition for the development of a nuclear clock of extremely high accuracy.
CdO is a basic oxide and is thus attacked by aqueous acids to give solutions of [Cd(H 2 O) 6] 2+. Upon treatment with strong alkaline solutions, [Cd(OH) 4] 2− forms. A thin coat of cadmium oxide forms on the surface of cadmium in moist air at room temperature. [12] Cadmium will oxidize at room temperatures to form CdO. [23]