The table does not lie

With genius intuition and daring, a young Russian professor, Dmitri Ivanovich Mendeleev, succeeded in creating a system that summarized the existing knowledge and allows even today a look into the future

February 8, 2016 – Invent while sleeping - about the birth of the idea of ​​the periodic table by Dmitri Mendeleev

Mendeleev's great victory was in predicting elements that had not yet been discovered in the databases of the American Chemical Society, which are considered the most comprehensive and up-to-date, with more than 30 million substances listed. But another database, in which one page, contains knowledge not only about the existing materials, but also about those that are yet to be created: "The periodic table of the elements".

The knowledge in it is infinite: it only takes a little understanding of the way it is organized and the principles of chemical bonding between atoms - and it still guides everyone who is involved in material science today. It is amazing to discover that the updated table of the year 2001, which lists 115 elements - including 23 man-made - is basically no different from the one devised by Dmitri Ivanovich Mendeleev in 1869, when the scientific world knew only 63 elements, and no one had any idea about the structure of the atom. Through ingenious intuition and courage, a young Russian professor managed to create a system that summarized the existing knowledge, linked facts and allows even today a look into the future.

Mendeleev's story began in the city of Tobolsk in Siberia, where he was born in 1834 as the eldest son of a family blessed with children (it is not clear whether he was the 14th child or the 17th). To his dismay, the boy had to focus on Greek and Latin at school. He was exposed to science in private lessons with a political activist who was exiled to Siberia and married one of the older sisters of the Mendeleev family. Apparently, in addition to a scientific education, his tutor-brother-in-law also received reinforcements for his willingness to dare and not submit to conventions. But later Mendeleev claimed that it was his mother who contributed the most to his education and the formation of his personality.

His father, a literature teacher, went blind near the birth of his youngest child. The burden of providing for the family was thus placed on his mother, who resourcefully began to operate a glass factory. Within one year, his father died and his mother's factory burned down, and the energetic woman decided to move to Moscow to nurture the obvious talents of Ben Zakonya. But the institutions of higher education in the big city locked their doors with the excuses of the lack of admission quota and an insufficient level of students from Siberia. The gates were also locked in St. Petersburg. When she realized that talent was not enough, she made connections: the director of the Central Pedagogical Institute in St. Petersburg was a friend of her late husband, and thus the young Mendeleev was accepted for studies.

Although it was not a university but rather a teacher's college, Mendeleev received excellent scientific training thanks to members of the university faculty who also taught at the college and allowed him to engage in research. After he qualified as a teacher, he won an honors scholarship that allowed him to study in the scientific centers of those days in France and Germany. When he returned to Russia he worked at a technical school and later was appointed professor of chemistry at St. Petersburg University. So he became a revered lecturer: in an enthusiastic and eccentric performance (with a mane of hair and a beard that he bothered to tell only once a year and a stormy temper that he inherited, according to him, from his Tatar ancestors) he presented innovations from the front of science, educated him in scientific thinking, and swept away many after him.

But something disturbed his rest. As a teacher, the lack of an updated chemistry book in Russian was impossible for him. He therefore decided to approach writing, but then he found himself forced to deal with the chaos that reigned in the world of chemistry. The 19th century was full of chemical activity and from its beginning to the middle of it, the number of known elements doubled. But the accumulated knowledge was accumulated, and Mendeleev came to the conclusion that he would not be able to write a proper book until he created an organized structure for the various elements.

Thus, for didactic considerations, he approached a scientific task that had been overlooked by many before him. Mendeleev's starting point, like his predecessors, was that the world cannot be based on a random collection of particles, and that the search for regularity in the properties of elements must be related to their arrangement in increasing atomic weight.

Mendeleev used to play solitaire on his long journeys from his home in the city to his estate in the countryside. He also approaches his research like a card game. For each element he prepared a card with its name and properties, and he laid out the 63 cards in ascending order of atomic weights: from the hydrogen atom, to which the value was attributed 1, to the element lead - whose atom is 207 times heavier than hydrogen. After that he tried to sort them according to different similarities, time and time again time.

And on Monday, February 17, 1869, all of a sudden, everything worked out. Mendeleev found that when the elements are arranged in ascending order of atomic weights, their properties change gradually and cyclically: after every few elements, an element reappears whose properties and behavior are similar to the element that appeared before. In his table, Mendeleev arranged the elements so that in the horizontal rows - "cycles" - the properties changed gradually; Whereas in the vertical columns - "families" - there were similar foundations.

How did Mendeleev succeed in a task where his predecessors failed, and why is his name identified with the periodic table while the German Luther Mayer, who presented a similar table at the time, appears in history as an appendix to his story?
The answer is complex. Just as it is difficult to put together a puzzle when pieces are missing, it was difficult to discover a pattern when the number of known elements was small, and some of the data was wrong. Thus, for example, according to the atomic weights known at the time, the element boron, B, should appear before beryllium, Be, but the chemical properties indicated the opposite order. Imbued with a belief in cycles and familiality, Mendeleev decided that there was a mistake in the weights and placed the elements in the order he considered correct. Experiments done later proved that he was right.

His great victory was in predicting elements that had not yet been discovered. For these Mendeleev left empty squares with question marks and predicted their properties. The correctness of his prophecies was first confirmed with the discovery of the element gallium in 1875. In the first report on gallium, a discrepancy was found in its specific weight, and there were those who used this to raise doubts about Mendeleev's ideas. But he stuck to his point, announced that the measurements were wrong - and again he was right.

Mendeleev felt the regularity even though he could not explain it. The explanation came after his death, when the structure of the atom was deciphered. It turned out that the periodicity in the chemical properties does not depend on the weights but on the atomic numbers, that is, on the number of protons found in the atomic nucleus. Fortunately for Mendeleev, with the exception of single cases, as the number increased, so did the weight. But he was much more than lucky: he saw the big picture, went to the light and did not let the anomalies distract him. Other scientists who tried to organize the elements were afraid of breaking a frame when an element did not fit in its place, did not engage in predicting elements and did not fight for their ideas as Mendeleev did. For this reason, it is Mendeleev's name - and not another name - that is still associated with the table to this day.

Mendeleev was a man of principles, and not only in his field of work. He supported the political organization of students and resigned in protest because the authorities rejected a petition he submitted for more freedom within the university. He did not withdraw and moved to work as the director of the Russian Standards Institute. Despite his other contributions to science, including the development of Russia's oil industries, he was never elected to the Russian Academy of Sciences.

However, even though he was at odds with the establishment, the Tsar showed him kindness. At the age of 48, he fell in love with a young student and married her before his divorce from his first wife was settled. Rumor has it that a Russian nobleman who fell into a similar situation of bigamy and was reprimanded by the Tsar, complained: "Why is Mendeleev allowed and I am not allowed?" The Tsar's response was "Mendeleev may have two wives, but I only have one".

The distribution of Nobel prizes began in 1901. Mendeleev's candidacy was submitted in 1905 and 1906, but he did not win the prize. The fact that he worked in Russia, far from the leading centers of science, did not help, as did the fact that until his death, in 1907, no explanation was found for the cyclical behavior. Is it his character and unorganized behavior that denied him the award, or did the world of science fail to appreciate vision and creativity?

* Dr. Hana Arzi is the director of Hamada, the center for scientific education in Tel Aviv

to the Hamada site

More on the subject on the knowledge website - as of February 2016

• Invent while sleeping - about the birth of the idea of ​​the periodic table by Dmitri Mendeleev
• The seventh row in the periodic table of the elements is complete
• Breaks in the periodic table
• A triumph of chemistry