A very unstable element

History often develops into myth. And the history of science is not strange to that phenomenon. Many of the individuals on whose shoulders we currently stand lived lives that have been romanticized and caricatured in public imagination. Beyond their universally recognized contributions to scientific knowledge, Darwin will always be associated to finches, and Newton to the apple fallen from the tree, even when it has been thoroughly proved that both stories have more in common with fiction than with reality. In this piece, I will write about one of these cases. Let me introduce you a Russian gentleman with a very keen interest on chemistry. Based on this description, you may have thought of President Vladimir Putin. Close, but not enough. In fact, radioactive substances were not the subject of research of our man. The person I am describing was born 100 years before the current Russian president. Let’s meet Dmitry Ivanovich Mendeleyev.

Mendeleyev was born on the 8^th of February of 1834 in the Siberian city of Tobolsk, the youngest of 14 children. His father, Ivan, was a moderately well-off school principal that married the heiress of a family of glass makers, which allowed the young Dmitry to receive a basic grasp of the science knowledge known at the time. However, Ivan tragically developed blindness and died soon after when Mendeleyev was 13. In order to provide another source of income, his mother other reopened the family glass factory, but that enterprise did not last long either, as the place burned down a few months after the reopening.

Thus, she decided to move the whole family to St. Petersburg. This is a distance comparable to that between London and Athens as the crow flies, a move that was complicated when one takes into account the travel logistics of a barely industrialised country such as the Imperial Russia of the time. Dmitry was enrolled in Main Pedagogical Institute in the city, and shortly thereafter his mother also passed away, leaving the young Mendeleyev an orphan. Despite this, he was able to overcome such personal tragedy, as he managed to graduate in 1855, when he turned 21. He went to complete a masters degree and a PhD by the time he turned 30. In fact, he was already a renowned chemist at the age of 25, having been invited to the International Conference of Karlsruhe that standardised atomic weights. During those years, he had started theorizing about a classification system for the known elements, and those efforts culminated in 1869 with the publication of his Principles of Chemistry.

First, some history. By the early 19^th century, Lavoisier and Dalton had respectively enunciated the law of mass conservation and the theoretical existence of atoms. In the course of the century, several new elements (considered at the time to be essential substances) had been isolated and their atomic weights measured. However, no satisfactory classification of the elements had been successfully formulated. The German chemist Johann Döbereiner had already theorized in 1817 the existence of triads of elements, such as Li, Na and K and F, Cl and Br, that shared similar chemical behaviour and appearance. The genius of Mendeleev was combining the two concepts (chemical and atomic weight) into one. The legend says that Mendeleev took inspiration from a game of solitaire; the truth is that, according to the man himself, the idea came to him in a dream where he saw the elements arranging themselves. And so, the periodic system was born.

The key of the periodic system is the periodic principle: the elements, if arranged according to their atomic weight, exhibit an evident periodic periodicity of properties (Scerri, 2006). Elements which have similar chemical behaviour have atomic weights that increase regularly. While undoubtedly atomic weight proved to be essential for the ordering, it did not overrule chemical properties (Br after Te). Nowadays we have abandoned the concept of atomic weight in favour of the atomic number (which increases linearly and in a fixed, discrete interval of 1) but it should be remembered that protons wouldn’t even be discovered till Rutherford’s experiments in the early 20^th century. The periodicity rule allowed him to predict the existence of elements that had not been yet discovered, such as Ge, which occupied gaps that had to contain something according to his theory.

While the periodic table and Mendeleev will always go hand in hand in the public’s consciousness, Mendeleev had a distinguished scientific career in areas outside periodicity. He was among the first to formulate the existence of the “absolute point of ebullition” (what we today call the critical point of a substance). He was a devoted science communicator, writing dozens of textbooks about physical, organic and inorganic chemistry. He was appointed by the Tsar as the Director of the Bureau of Weights and Measurements, which was instrumental for the introduction of the metric system to Russia.

Nonetheless, as he grew older, Mendeleev’s behaviour started to become more erratic. He divorced his wife and married a woman 20 years his junior, which made him a bigamist in the eyes of the Russian Orthodox Church. His hair and beard grew long as he refused to have them cut more than once a year, giving him the looks of the long-lost child of Marx and Bakunin. These eccentricities moved into the realm of sciences: he dismissed radioactivity, stating that its supposed effects were instead caused by a yet to be discovered element that he linked to the ancient Greek concept of aether, a mysterious substance that could supposedly be found in the astral bodies. His disagreements with Svante Arrhenius’s theory of the ionic dissociation of solutions proved to be more fundamental for Mendeleev’s career, as the Swedish chemist never forgot his criticism and lobbied furiously in the Swedish Academy of Sciences against awarding the Chemistry Nobel Prize to the Russian scientist. Arrhenius was successful, as Dmitry Mendeleev died on the 2^nd of February of 1907 in St. Petersburg, celebrated in his country and abroad, but without a Nobel.

This historical injustice was corrected a century later by the International Union of Pure and Applied Chemistry (IUPAC), the scientific body that names newly discovered elements. Indeed, element 101 was baptised as Mendelevium, a homage to the chemist that wove the elements together. Ironically, Mendelevium is a radioactive element whose most abundant isotope has a half-life of 51 days, but this ties it to the individual that lent his name to it. After all, both of them were very unstable elements.

Mendeleev’s legacy also remains in more subtle ways that nonetheless proved to be pivotal for the advance of science. It can be argued that his popularisation of sciences in his home country paved the way for the research of Landau, Oparin and Korolev. The accomplishments of Soviet science in the 20^th century, among them sending a man to outer space for the first time in history may have not occurred without the work laid by the bearded genius. That, and nothing else, is the myth that deserves to become immortal.

Scerri, E. (2006) The Periodic Table: Its Story and Significance. New York, Oxford University Press

Juan Rubio Gorrochategui is studying for a MSc in Science Communication at Imperial College London.

Banner image: DIMendeleev, Wikipedia Commons