To date, the letters of Abu Rayhan Biruni and ibn Sina have been preserved, along with their works, where scientists also debated on the topic of the structure of matter. According to the assumption of scientists, the world consisted of particles smaller than an atom, it is there that one can see the assumptions that the atom particle, which was then considered indivisible, is divisible, but not to infinity. As for their shape, then it was assumed that the atoms have a spherical shape, since the sphere was considered a kind of ideal model, therefore, the atoms should be like this.
Time passes and a variety of discoveries are made. But about the ideas of Epicurus, however, as well as about atomism, they forget, because the ideas of Epicurus contradicted Christian teachings and the church forbade its use, as well as the assertion that atoms exist. But the French Catholic priest Pierre Gassendi revived the idea of atomism, somewhat changing the notion that atoms were created by God. And after the defense of atomism by the chemist Robert Boyle an outstanding chemist and author of the work "The Skeptical Chemist", as well as by Sir Isaac Newton, who himself was revered as an outstanding scientist, atomism was adopted by the end of the 17th century.
Let us quote Sir Newton himself on this topic from a translation of his works: "It seems to me that from the very beginning God created matter in the form of solid, weighty, impenetrable, mobile particles and that he gave these particles such dimensions, such shape and such other properties and created them in such relative quantities as he needed it was for the purpose for which he created them. These primary particles are absolutely solid: they are immeasurably harder than the bodies that consist of them so hard that they never wear out and do not break into pieces, because there is no such force that could divide into parts what God himself created inseparable and whole on the first day of creation. Precisely because the particles themselves remain intact and unchanged, they can form bodies that have the same nature and the same structure forever and ever; for if the particles were worn out or broken into pieces, the nature of things depending on them would change. Water and earth, made up of old, worn-out particles and fragments, would differ in structure and properties from water and earth, built from still whole particles at the beginning of creation. Therefore, in order for nature to be durable, all changes in the bodies of nature can consist only in a change of location, in the formation of new combinations and in the movements of these eternal particles God could create particles of matter with different sizes and can have different shapes, place them at different distances from each other, endow them, perhaps, with different densities and different acting forces. In all this, at least, I do not see any contradictions So, apparently, all bodies were built from the above-mentioned solid impenetrable particles, which were placed in space on the first day of creation at the direction of God's mind."
And if at that time Boyle's ideas were established that there are "simple bodies" (chemical elements) and "perfect mixtures" (chemical compounds) and any "perfect mixtures" can be divided into "simple bodies", then in the book "The New System of Chemical Philosophy" of 1808, John Dalton put forward the first idea about which of the substances, to which type is subject. But before that, Lavoisier proved that mass is constant, it does not disappear anywhere and does not appear out of nowhere. Davy also discovered a number of chemical elements: hydrogen, oxygen, nitrogen, carbon, sulfur, phosphorus, sodium and potassium were discovered by him in 1807, and in 1808 he also discovered such elements as calcium, strontium, barium and magnesium. Iron, zinc, copper, lead, silver, platinum, gold and mercury were also discovered.
Their discovery did not take much more work, since many of them were isolated from ores, isolated from chemical compounds. And already water, ammonia, carbon dioxide and many other compounds were already considered perfect mixtures. And now, Dalton, having everything he needed, decided to determine the atomic masses of all chemical elements, and also enter them all into tables, that is, classify them. So, Dalton introduced his own designation for each chemical element, for example, for hydrogen he introduced a circle icon with a dot in the center, for oxygen there was a sign an ordinary circle, and for carbon there was a sign of a painted black circle, etc. To calculate the masses of atoms, Dalton conducted some experiments.
Initially, he evaporated water, and on the upper part he installed substances with which hydrogen reacted better, calculating changes in both the mass of the substance with which the interaction took place or from the volume of steam, Dalton could determine which part of the water consists of hydrogen and which of oxygen. Thus, having determined that 1/8 of the total mass of water consists of hydrogen, and 7/8 of oxygen, Dalton decided that oxygen is heavier than hydrogen and assigned a mass equal to 1 to hydrogen and 7 to oxygen. The same analysis of ammonia showed 1 for hydrogen and 5 for nitrogen. After analyzing it in this way, Dalton compiled his own table of chemical elements.
Needless to say, although this was the first step on the path of knowledge, all these statements were not true. But it lasted for quite a long time and various assumptions were based on it. One of these hypotheses was published in the journal "Philosophical Annals" by the London physician William Prout and was devoted to the idea that all atoms consist of hydrogen. But of course, this hypothesis was not true like many other assumptions of that time.
And if then, the atomic unit of mass was taken as the mass of a hydrogen atom, then today the exact unit is considered to be 1/12 of the mass of a carbon atom and is named as an A. E. M. or atomic unit of mass. And chemical elements today are usually designated from the first two or one letter of their name in Latin, for example, hydrogen is designated as H due to the name Hydrogenium («Generating water» in Latin), Nitrogen N or Nitrogenium «Giving birth to saltpeter», iron Fe or Ferrum, copper Cu Cuprum, carbon C Carboneum. This system was adopted on September 3, 1860 after the Italian chemist Stanislao Cannizzaro at the International Congress in Karlsruhe proposed this method in his speech.
After that, it was customary to record chemical compounds using these symbols, and the number of atoms was indicated in the lower right corner, so for example, the compound of carbon and hydrogen (water) is written as H2O, ammonia NH3, sulfuric acid H2SO4, etc. This method is very convenient because it creates opportunities for using symbolic notation and not there is no need to write down all the symbols several times, for example, for a cane sugar molecule C6H12O6 (6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms). Instead of CCCCCCHHHHHHHHHHHOOOOOO, you can easily and simply write C
6
12
6
If everything is already clear with the notation, then there remains one very interesting consequence. Taking into account the fact that 1 atomic unit of mass is equal to 1/12 of a carbon atom, this makes it possible to calculate the masses of all chemical elements using compounds with carbon. For a better explanation, lets give an example. Suppose there is a certain compound of carbon and hydrogen, if you act on it with an electric current or heat it, then it is possible, if it is solid, to melt, if the liquid is evaporated and to obtain a finite volume of carbon and hydrogen. From the ratio of their masses and volumes, it is possible to determine how many hydrogen atoms account for one carbon atom, and already from the ratio of their masses, it is possible to calculate the mass of hydrogen. So if we divide the methane compound into carbon and hydrogen, we get 4 times more hydrogen than carbon in volume, so we can conclude that for 1 carbon atom, there are 4 hydrogen atoms and the CH