172 is the atomic number of the yet undiscovered element directly below ra in the periodic table.
172 is the atomic number of the yet undiscovered element directly below ra in the periodic table.
what is the atomic number of the yet undiscovered element directly below ra in the periodic table?
172
seaborg's subsequent elaborations of the actinide concept theorized a series of superheavy elements in a transactinide series comprising elements from 104 to 121 and a superactinide series of elements from 122 to 153. he proposed an extended periodic table with an additional period of 50 elements (thus reaching element 168); this eighth period was derived from an extrapolation of the aufbau principle and placed elements 121 to 138 in a g-block, in which a new g subshell would be filled. seaborg's model, however, did not take into account relativistic effects resulting from high atomic number and electron orbital speed. burkhard fricke in 1971 and pekka pyykkö in 2010 used computer modeling to calculate the positions of elements up to "z" = 172, and found that the positions of several elements were different from those predicted by seaborg. although models from pyykkö, fricke, and nefedov "et al." generally place element 172 as the next noble gas, there is no clear consensus on the electron configurations of elements beyond 120 and thus their placement in an extended periodic table. it is now thought that because of relativistic effects, such an extension will feature elements that break the periodicity in known elements, thus posing another hurdle to future periodic table constructs.
history of the periodic table
following the discovery of the atomic nucleus by ernest rutherford in 1911, it was proposed that the integer count of the nuclear charge is identical to the sequential place of each element in the periodic table. in 1913, henry moseley using x-ray spectroscopy confirmed this proposal experimentally. moseley determined the value of the nuclear charge of each element and showed that mendeleev's ordering actually places the elements in sequential order by nuclear charge. nuclear charge is identical to proton count and determines the value of the atomic number ("z") of each element. using atomic number gives a definitive, integer-based sequence for the elements. moseley predicted, in 1913, that the only elements still missing between aluminium ("z" = 13) and gold ("z" = 79) were "z" = 43, 61, 72, and 75, all of which were later discovered. the atomic number is the absolute definition of an element and gives a factual basis for the ordering of the periodic table. in other words, since the atomic number of an element is the same as the number of protons in its nucleus, the modern periodic table arranges the elements according to their atomic number, and relative to their atomic mass, the way mendeleev did. the periodic table is used to predict the properties of new synthetic elements before they are produced and studied.
periodic table