A paper published this week in Physical Chemistry Chemical Physics maps out 54 unknown chemical elements that could lie beyond element 118, ununoctium. Mendeleev’s original classification of the elements into groups and periods is underpinned by chemical quantum mechanics, which describes the interactions of electrons and protons and dictates the electronic structures of the elements. There are no new elements to be found within the conventional Periodic Table as elements of atomic number 1-118 have all been accounted for however fleetingly some might exist.
Now, Pekka Pyykkö has applied computational model to predict the electronic structures for elements with more than 118 protons, up to 172, in fact. This stretches way beyond the limits of current synthetic methods for making the highly unstable heavy elements at the bottom right of the Periodic Table. Pyykkö’s calculations also hint at the possible chemistry of the elements as far as it could go given their likely ultrashort halflives.
The extra 54 super heavy elements predicted by Pyykkö may exist under extreme conditions with very short lifetimes due to radioactive decay. Conversely, there might be stable elements with these atomic numbers that have simply not been formed because the extreme conditions needed have not yet been observed. The work shows how the rules of quantum mechanics and relativity function in determining chemical properties, says Pyykkö, such as the potentially record-high oxidation states that he predicts.
Pekka Pyykko (2010). A Q1 suggested periodic table up to Z r 172, based on Dirac–Fock calculations on atoms and ions Phys Chem Chem Phys