by David Salazar Marcano
Article originally published in Science@Leuven
Of course, this title is not in accordance with the Chinese Zodiac Calendar, but was actually declared by the United Nations General Assembly and UNESCO.
But why has 2019 been awarded such a scientific distinction? Well, the Periodic Table of Elements, a familiar symbol of modern science which is recognisable to even the untrained eye, was initially postulated 150 years ago by the Russian chemist Dmitri Mendeleev. Hence, for the 150th anniversary of its discovery, several events will be taking place across the world to celebrate The International Year of the Periodic Table including an opening ceremony on the 29th of January in Paris (more information on this and other events at https://www.iypt2019.org/
However, as accustomed as we might be to Mendeleev’s table due to its almost ubiquitous presence in classrooms and labs as well as its popularity on merchandise such as mugs, table cloths, and posters there is much more to it than meets the eye. For one, it has not remained the same since its invention. Multiple elements have been discovered and added over the years, up to the latest addition of the heaviest known element 118 (Oganesson, Og) which was only formally named in November of 2016 in honour of the Russian physicist Yuri Oganessian. Secondly, few of us have actually stopped to consider the reason for its strange shape, seemingly created by playing Tetris with the elements.
In fact, the periodic table actually exists in several other shapes since a large variety of other ways of organising the elements have been used to emphasise different trends over the years. A vast repertoire of all periodic tables which have been created for different purposes is available on The Internet Database of Periodic Tables.
One such alternative and an unconventional periodic table of interest is the Left-step periodic table proposed by French engineer Charles Janet in 1928. Although Mendeleev’s table has gained widespread popularity, last December Dr. Pieter Thyssen expressed a distinct preference for this particular periodic table over its more popular counterpart in his lecture on The Periodic Table and the Quest of the Philosopher’s Stone of Quantum Alchemy, organised by The Royal Flemish Chemical Association (KVCV) at KU Leuven’s Chem&Tech building. As its name suggests, the Left-step periodic table looks like a staircase with steps going up from left to right towards Hydrogen and Helium at the top. This layout gives it an admittedly much more organised appearance than the standard form above.
However, aesthetics is not the main reason for choosing to present the elements in this manner. More importantly, the Left-step periodic table organises the elements based on how the energy levels of its atoms are filled by electrons where the number of the period or row an element occupies corresponds to the value “n+l” for its outer-shell electrons (where “n” and “l” are quantum numbers that define the energy of the electrons). Nevertheless, a question still remains: why does the periodic table, in any of its multiple forms, display the patterns that it does?
Such is the issue that Dr. Thyssen tackled during his PhD at KU Leuven under Prof. Koen Binnemans (2009-2013). The answer he found lies in Group Theory: the mathematical tool he used in order to try to expose the hidden symmetry of the periodic table. These were the secrets he revealed in his December lecture by engaging in a mathematical game of chess, first with the Hydrogen atom and then with the whole table of elements. Unlike a normal game of chess, this one involved first passing through the fourth dimension in order to see symmetries invisible to us in our 3D world.
Indeed, thinking in any higher dimension than three might seem like a daunting task. Especially for those of us unfamiliar with group theory or even chess, the mere thought of just following such a game would seem overwhelming - but somehow Dr. Thyssen manages to guide you through the whole process in a very elegant and approachable manner so as to eventually be able to represent all the elements as a state of one super element. This super element has a particular mathematically-defined symmetry group that can be subdivided into other groups as the symmetry is broken. Hence, as Dr. Thyssen explains “mathematically there is a way to transmute any element into any other element.” Indeed, Group Theory would allow you to convert Lead into Gold!
Unfortunately for the aspiring Alchemists, this is only easy on paper and does not mean it can actually be done that simply in practice. But for those who would like to give it a go anyway Dr. Thyssen’s book on the matter – Shattered Symmetry: From the Eightfold Way to the Periodic Table – will guide you step by step on how to do it. Yet, this book only unveils but some of the mysteries that still remain concealed within the Periodic Table of Elements, even after 150 years. Not only is the Periodic Table an incredibly useful tool but it also represents a chronicle of scientific advancements over the years and a source of inspiration for future discoveries.
Dr. Thyssen’s The Periodic Table and the Quest of the Philosopher’s Stone of Quantum Alchemy Lecture is on December 12th 2018.
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