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When the Russian chemist Dmitri Mendeléyev (1834-1907) created his periodic table, observed that the sequence did not coincide and correctly deduced that there were elements that had not yet been discovered.
To name them he used three Sanskrit words: eka (one), two (two and tri (three). With them the first, the second and the third element below a known one were indicated, respectively.
An open window to oncology
Gold is yellow, lithium white, silver has a bright light gray coloration but the astato (At) is so rare that we don’t even know what its color is. This element, with atomic number 85, is located below the iodine (corresponded to Mendeleev’s ekaiode) and is the least abundant on Earth, to the point that it is calculated that at a given instant there is less than one gram.
In addition to being scarce, it is very unstable, it has a disintegration period of just over seven hours. To these oddities we must add another singularity, astatine is a radioactive element, which forces laboratories to work with very high safety standards. However, and this is truly important, radioactivity may represent an opportunity, since according to recent research, thanks to it, it could be postulated as a revolutionary cancer treatment.
The isotope 211-At could be used as a radiopharmaceutical since its nucleus is capable of releasing energy in the form of alpha particles that could be deposited in a space of approximately 0.05 mm, the diameter of a cancer cell.
His discovery was quite an odyssey
During the thirties and forties of the last century many researchers launched after its discovery. One of the first was Fred Allisonwho claimed to have found it and whom he baptized as ‘alabamine‘. Some time later the method used was found to be incorrect and consequently the discovery of him was disavowed.
The next to think they had found it were Horia Hulubei e Yvette Cauchoisafter analyzing mineral samples using X-rays. They christened the element ‘dor’, but the scientific community did not accept that discovery as good either.
The third parties in the fight were Walter Minder and Alice Leigh-Smit, who in 1942 made public the discovery of the ‘helvetium’, which they later called ‘anglohelvetium’. However, neither the method nor the finding were accepted.
Since there are not three without four, the next and final turn fell to Traude Bermert and Berta Karlik |who not only synthesized astatine, but also managed to artificially produce 211-At.
A disciple of Marie Curie
Just two places from astatine in the periodic table is the francio (Fr), the second rarest chemical element on Earth, it is estimated that the amount of this alkali metal in the earth’s crust does not exceed thirty grams. It is a very radioactive chemical element that generates astatine, radium and radon in its disintegration.
Its discovery took place in 1939 thanks to the work of Marguerite Chaterine Pereya researcher who was a direct collaborator of Marie Curie. She got it while purifying samples of lanthanum that contained actinium. In this way, francium became the last natural element left to be discovered in Mendeleev’s periodic table of ninety-two elements.
There are currently no commercial applications for francium, due to both its scarcity and its instability. It is used exclusively in research, especially in the field of spectroscopy.
Pedro Gargantilla is an internist at El Escorial Hospital (Madrid) and the author of several popular books.