Everything material that surrounds us in nature, whether it be cosmic objects, ordinary earthly objects, or living organisms, consists of substances. There are many varieties of them. Even in ancient times, people noticed that they are able to not only change their physical state, but also turn into other substances endowed with other properties compared to the original. But here the laws according to which such transformations of matter take place, a person did not immediately understand. In order to do this, it was necessary to correctly identify the basis of the substance and classify the elements existing in nature. This became possible only in the middle of the 19th century with the discovery of the periodic law. Stories of its creation D.I. Mendeleev was preceded by many years of work, and the centuries-old experience of all mankind contributed to the formation of this kind of knowledge.
When were the foundations of chemistry laid?
Craftsmen of ancient times have succeeded quite well in casting and smelting various metals, knowing the many secrets of their transmutation. They passed on their knowledge and experience to descendants, who used it until the Middle Ages. It was believed that base metals could well be turned into valuable, which, in fact, was the main task of chemists until the 16th century. In essence, the philosophical and mystical ideas of the ancient Greek scholars that all matter is built from certain “primary elements” capable of transforming one into another were laid in a similar idea. Despite the apparent primitiveness of this approach, it played a role in the history of the discovery of the Periodic Law.
Panacea and White Tincture
Pursuing the search for the fundamental principle, alchemists firmly believed in the existence of two fantastic substances. One of them was a philosopher's stone glorified in legends, also called a life elixir or panacea. It was believed that such a tool was not only a reliable way to turn mercury, lead, silver and other substances into gold, but also served as a miraculous universal medicine that heals any human ailments. Another element, called the white tincture, was not so effective, but was endowed with the ability to convert other substances into silver.
In telling the backstory of the discovery of the periodic law, it is impossible not to mention the knowledge accumulated by alchemists. They embodied a pattern of symbolic thinking. Representatives of this semi-mystical science created a certain chemical model of the world and the processes taking place in it at the cosmic level. In an effort to understand the essence of all things, they wrote down laboratory techniques, equipment and information about chemical glassware in great detail, with great scrupulousness and diligence in transferring their experience to colleagues and descendants.
The need for classification
By the volume of information on a wide variety of chemical elements by the 19th century, enough was accumulated, which gave rise to the natural need and desire of scientists to systematize them. But to carry out such a classification, additional experimental data were required, as well as not mystical, but real knowledge about the structure of substances and the essence of the basis of the structure of matter, which did not exist yet. In addition, the available information on the value of atomic masses of the chemical elements known at that time, on the basis of which systematization was carried out, did not differ with particular accuracy.
But attempts to classify among natural scientists have been repeatedly undertaken long before the realization of the true essence of things, which is now the basis of modern science. And many scientists worked in this direction. Speaking briefly about the prerequisites for the discovery of the periodic law of Mendeleev, we should mention examples of such associations of elements.
Triads
Scientists of those times felt that the properties manifested by a wide variety of substances are in an undeniable dependence on the values ​​of their atomic masses. Understanding this, a chemist from Germany Johann Döbereiner proposed his own system for classifying the elements that make up the basis of matter. It happened in 1829. And this event was quite a serious advance in science for that period of its development, as well as an important stage in the history of the discovery of the periodic law. Doebereiner united the known elements into communities, giving them the name "triad." According to the existing system, the mass of the extreme elements turned out to be equal to the average of the sum of the atomic masses of that member of the group that was between them.
Attempts to expand triad boundaries
There were enough flaws in the mentioned Döbereiner system. For example, in the chain of barium, strontium, calcium there was no magnesium similar in structure and properties to them. And in the community of tellurium, selenium, sulfur, there was not enough oxygen. Many other similar substances also could not be classified according to the triad system.
These ideas tried to develop many other chemists. In particular, the German scientist Leopold Gmelin sought to push the "tight" framework by expanding the groups of classified elements, distributing them in the order of equivalent weights and electronegativity of the elements. Its structures formed not only triads, but also tetrads, pentads, but the German chemist was not able to grasp the essence of the periodic law.
Spiral de Chancourtois
Alexander de Chancourtois came up with an even more complicated scheme for constructing elements. He arranged them on a plane rolled into a cylinder, distributing them vertically with a slope of 45 ° in the order of increasing atomic masses. As suggested, along lines parallel to the axis of the given volumetric geometric figure, substances with similar properties should be located.
But in reality, an ideal classification did not work out, since by no means related elements sometimes fell on one vertical. For example, next to alkali metals was a completely different chemical behavior of manganese. And sulfur, oxygen, and completely different element titanium with them, got into one “company”. However, such a scheme also contributed, taking its place in the history of the discovery of the periodic law.
Other attempts to create classifications
Following the description, John Newlands proposed his classification system, noting that every eighth member of the resulting series exhibits similar properties in the elements arranged in accordance with the increase in atomic mass. It occurred to the scientist to compare the found regularity with the arrangement of musical octaves. At the same time, he assigned each of the elements his own serial number, placing them in horizontal rows. But such a scheme again did not turn out to be ideal and was evaluated very skeptically in scientific circles.
From 1964 to 1970 tables ordering chemical elements were also created by Odling and Meyer. But such attempts again had their drawbacks. All this happened already on the eve of the discovery of the periodic law by the Mendeleev. And some works with imperfect classification attempts were published even after the table that we still use today was presented to the world.
Biography of Mendeleev
A brilliant Russian scientist was born in Tobolsk in 1834 in the family of the director of the gymnasium. In the house, besides him, there were sixteen other brothers and sisters. Not deprived of attention, like the youngest of children, Dmitry Ivanovich from a very small age hit everyone with extraordinary abilities. Parents, despite the difficulties, sought to give him the best education. So, Mendeleev first graduated from a gymnasium in Tobolsk, and then the Pedagogical Institute in the capital, while retaining a deep interest in the sciences in his soul. And not only in chemistry, but also in physics, meteorology, geology, technology, instrumentation, aeronautics and others.
Soon, Mendeleev defended his thesis and became an assistant professor at St. Petersburg University, where he lectured in organic chemistry. In 1865, he presented to his colleagues his doctorate on the topic "On the connection of alcohol with water." The year of the discovery of the periodic law was 1969. But this achievement was preceded by 14 years of hard work.
About the great discovery
Given the mistakes, inaccuracies, as well as the positive experience of colleagues, Dmitry Ivanovich was able to systematize the chemical elements in the most convenient way. He also noted the periodic dependence of the properties of compounds and simple substances, their form, on the value of atomic masses, as indicated in the formulation of the periodic law given by Mendeleev.
But such progressive ideas, unfortunately, did not immediately resonate in the hearts of even Russian scientists, who took this innovation very cautiously. And among the figures of foreign science, especially in England and Germany, the law of Mendeleev found all the most ardent opponents. But very soon the situation changed. What was the reason? After some time, the brilliant courage of the great Russian scientist appeared to the world in evidence of his brilliant ability of scientific foresight.
New elements in chemistry
The discovery of the periodic law and the structure of the periodic table created by him made it possible not only to systematize substances, but also to make a number of predictions about the presence in nature of many elements unknown at that time. That is why Mendeleev managed to put into practice what other scientists could not do before him.
Only five years passed, and the guesses of the great Russian chemist began to be confirmed. Frenchman Lecock de Bouabodran discovered a new metal, which he called gallium. Its properties turned out to be very similar to those predicted by Mendeleev in the theory of ecaaluminium. Learning about this, the representatives of the scientific world of those times were stunned. But the amazing facts did not end there. Further, Scandium was discovered by the Swede Nilson, a hypothetical analogue of which was ecabor. And the ecasilicia became the twin discovered by Winkler Germany. Since then, the law of Mendeleev began to be approved and gain new supporters.
New facts of brilliant foresight
The creator of the periodic system was so carried away by the beauty of his idea that he took the liberty of making some assumptions, the validity of which was later most brilliantly confirmed by practical scientific discoveries. For example, Mendeleev arranged some substances in his table not at all in accordance with the increase in atomic masses. He foresaw that periodicity in a deeper sense is observed nevertheless not only in connection with an increase in the atomic weight of elements, but also for another reason. The great scientist guessed that the mass of an element depends on the quantity in its structure of some more elementary particles.
Thus, the discovery by Mendeleev of a periodic law in some way prompted the representatives of science to think about the components of an atom. And scientists of the approaching 20th century - the century of grandiose discoveries - were convinced many times that the properties of elements depend on the magnitude of the charges of atomic nuclei and the structure of its electron shell.
Periodic law and modernity
The periodic table, while remaining unchanged at its core, was subsequently repeatedly supplemented and redone. It formed the so-called zero group of elements, which includes inert gases. The problem of the placement of rare-earth elements was also successfully solved. But despite the additions, the significance of the discovery of Mendeleev’s periodic law in the initial version is difficult to overestimate.
Later, with the discovery of electrons and the phenomenon of radioactivity, the reasons for the success of such a systematization, as well as the periodicity of the properties of elements of various substances, were fully understood. Soon, the isotopes of radioactive elements also found their place in this table. The basis for the classification of numerous cell members is the atomic number. And in the middle of the 20th century, the sequence of the arrangement of elements in the table was finally justified, depending on the filling of the atom’s orbitals with electrons moving at great speed around the nucleus.