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Protactinium is a chemical element; it has symbol Pa and atomic number 91. It is a dense, radioactive, silvery-gray actinide metal which readily reacts with oxygen, ...
The most stable isotope is 231 Pa with a half-life of 32,760 years, 233 Pa with a half-life of 26.967 days, and 230 Pa with a half-life of 17.4 days. 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.
Protactinium forms borohydrides which include Pa(BH 4) 4. It has an unusual polymeric structure with helical chains where the protactinium atom has coordination number of 12 and is surrounded by six BH 4 − ions. [20]
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
Protactinium-233 has a half-life of 27 days and beta decays into uranium-233; some proposed molten salt reactor designs attempt to physically isolate the protactinium from further neutron capture before beta decay can occur, to maintain the neutron economy (if it misses the 233 U window, the next fissile target is 235 U, meaning a total of 4 ...
229 Pa synth: 1.5 d: ε: 229 Th: 230 Pa ... The number willbe rounded to 3 sigfig. ... ACTION: Two protons ejected from nucleus simultaneously. QID: double proton ...
Two protactinium oxides have been obtained: PaO 2 (black) and Pa 2 O 5 (white); the former is isomorphic with ThO 2 and the latter is easier to obtain. Both oxides are basic, and Pa(OH) 5 is a weak, poorly soluble base. [93] Decomposition of certain salts of uranium, for example UO 2 (NO 3)·6H 2 O in air at 400 °C, yields orange or yellow UO ...
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