Scientists propose a new way of ordering elements: Bestgamingpro



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The periodic table of the elements, created mainly by the Russian chemist Dmitry Mendeleev (1834-1907), celebrated its 150th anniversary last year. It would be hard to overstate its importance as an organizing principle in chemistry: all budding chemists know it from the earliest stages of their education.

Given the importance of the table, one could be forgiven for thinking that the ordering of the elements was no longer the subject of debate. However, two scientists in Moscow, Russia recently published a proposal for a new order.

Let’s first consider how the periodic table was developed. By the end of the 18th century, chemists were clear about the difference between an element and a compound: the elements were chemically indivisible (examples are hydrogen, oxygen) while the compounds consisted of two or more elements in combination, with properties quite distinct from their component elements. In the early 19th century, there was good circumstantial evidence for the existence of atoms. And in the 1860s it was possible to list the known elements in order of relative atomic mass, for example hydrogen was 1 and oxygen was 16.

Simple lists, of course, are one-dimensional in nature. But the chemists were aware that some elements had quite similar chemical properties: for example lithium, sodium and potassium or chlorine, bromine and iodine. Something seemed to repeat itself and by placing chemically similar elements next to each other, a two-dimensional table could be built. The periodic table was born.

Importantly, Mendeleev’s periodic table was derived empirically based on the observed chemical similarities of some elements. It would not be until the early 20th century after the structure of the atom was established and following the development of quantum theory that a theoretical understanding of its structure would emerge.

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The elements were now sorted by atomic number (the number of positively charged particles called protons in the atomic nucleus), rather than by atomic mass, but still also by chemical similarities. But the latter now derived from the arrangement of electrons repeating themselves in the so-called “shells” at regular intervals. In the 1940s, most textbooks featured a periodic table similar to what we see today, as shown in the following figure.