the number and arrangement of their electrons), their chemical behaviour, their solubility, or their occurrence in geological deposits. The atoms can be subdivided according to the electron configuration (i.e. For them, there is no unambiguously correct arrangement of the elements depending on the criterion applied for classification, a different periodic table results. Guillermo Restrepo and Wilmer Leal from the Max Planck Institute for Mathematics in the Sciences and the University of Leipzig are not surprised. If one takes a closer look, one will discover slightly different variants of the periodic table in classrooms, lecture halls, and textbooks. For example, the correct position of lanthanum and actinium is debated. But appearances can be deceptive because many things still remain controversial: Scientists do not agree on exactly which elements belong in the third group below scandium and yttrium. © Guillermo Restrepo, MPI for Mathematics in the SciencesĪt first glance, the periodic table seems to have brought an unambiguous and final order to the currently known 118 elements. The elements are also classified into groups: Atoms in the same column usually have the same number of electrons in their outer shell. Today they are sorted by atomic number (which indicates the number of protons in the atomic nucleus) from the light hydrogen (one proton) to the exotic oganesson (118 protons). The tabular overview is closely linked to Dmitri Mendeleev and Lothar Meyer – two researchers who, in the 1860s, created an arrangement of elements based on their atomic masses and similarities. It is an icon of natural science and hangs in most chemistry classrooms: the periodic table of elements, which is celebrating its 150th birthday this year. The mathematical approach of the Leipzig scientists is very general and can provide many different periodic systems depending on the principle of order and classification – not only for chemistry, but also for many other fields of knowledge. This is the conclusion reached by researchers at the Max Planck Institute for Mathematics in the Sciences in Leipzig and the University of Leipzig in a recent paper. This tabular overview of the chemical elements, which goes back to Dmitri Mendeleev and Lothar Meyer and the approaches of other chemists to organize the elements, involve different forms of representation of a hidden structure of the chemical elements. Now that does make a bit more sense.The periodic table of elements that most chemistry books depict is only one special case. Now, the table is called the periodic table because the elements with similar properties occur at regular intervals.Ĭal: Ah, OK. Mrs Roberts: Well, elements that have similar properties to each other are put into vertical columns called groups. The way we arrange them is in the order of increasing atomic number.Ĭal: And what about these vertical columns? I mean, what does all of that mean? It has changed a lot over the years as we've learned more and more about atoms. Mrs Roberts: Well, the modern periodic table shows us all of the elements arranged in rows, which are called periods. So how has the periodic table been put together? OK, well I might have been able to find that, but I'm still a little bit lost on what all of this actually means. See if you can see it in the periodic table.Ĭal: OK. Mrs Roberts: So, the chemical symbol is Al. And what is the chemical symbol for aluminium? Now, each element has a chemical symbol made of one or two letters.Ĭal: Right, OK. Mrs Roberts: So, here I have an empty pop can. Cal: Let's talk about some of the elements on the periodic table, shall we?
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