We have a modern periodic table
On the history of the periodic table of the elements
Prof. Dr. rer. nat. Peter Buck
Anyone who wants to study the periodic table of the chemical elements is well advised to know that the word 'element' is used here in two completely different meanings: On the one hand, the 'element gold' means the shiny yellow, the electric current Excellent conductive material that melts at 1064 ° C and is specifically very heavy. Its density is 19.32 grams per cubic centimeter. And without warning, the “element gold” also means the gold atom, which cannot have a melting point and also does not conduct electricity, which in itself has no color in the sense that we understand color, but only creates color when very many atoms come together to form particles or portions of material. Then gold can be red or green or shiny yellow, viewed in daylight. The consideration of the elementary substances was in the foreground in the nineteenth century when the periodic table of the elements was developed. The consideration of the elementary atoms did not come into focus until the twentieth century.
Modern periodic systems of the elements contain information about elementary substances such as boiling point, melting point, density, metal, non-metal and also information about the elementary atoms such as proton number, electron configuration or electronegativity. Every elementary substance is in principle made up of just like atoms. No substance is exactly 100% pure; The record for purity is held by silicon with a purity of 99.9999999999%. That means: here every quadrillionth atom is a foreign atom.
The Englishman Robert Boyle (1627–1691) can be regarded as the founder of modern chemistry: He was the first to classify acids as the substances that color blue plant pigment extracts red and dissolve marble. Bases were able to reverse this process. He was also the one who convincingly demonstrated that there had to be a lot more elements than four elements, i.e. water, earth, fire and air, in order to explain the diversity of substances and that one had to designate those uniform substances as an element, which can no longer be converted into two different other substances in any way. It is well known that hydrogen plus oxygen can be obtained from water (alone), from lime burnt lime plus carbonic acid (today's name: carbon dioxide). But sulfur (alone) always remains only sulfur, no matter how high you heat it or how tricky you try to electrolyze it.
The French Antoine Lavoisier (1743–1794) adopted Boyle's definition of the element (without naming him), but he had a different, broader conception of the element. He made a differencematière' and 'principe'. The matière appears: the matière sulfurique, the sulfur matter is yellow and melts into a yellow, later red liquid. But they are in sulfuric acid principe sulfurique, the sulfur principle, along with that principe oxygènique, the acid-generating principle, effective. The principe sulfurique gives sulfuric acid the individual properties that make sulfuric acid Principe oxygènique gives it the general acidic properties.
For Lavoisier there were no fabrics in which matière and principe coincided, because all substances were compounds of principe caloriquebecause all substances contained heat. The temperature was an indicator of "excess" principe caloriqueAt the transition of the aggregate states, defined quantities could calorique but can also be chemically bound (or become “latent”). Lavoisier therefore regarded all gases as strong calorique-containing substances. According to Lavoisier, it also contains sulfuric acid Principe oxygènique (the "acid generating" principle), which determines the type of substance, and the principesulfurique, which determines the individuality of this special acid, plus that principe calorique to varying degrees, depending on how hot or cold the matière is.
When the so-called imponderable substances heat, light and electricity were no longer viewed as substances, but as "forces" (energies), the German Julius Robert Mayer (1814–1878) claimed priority for this thought, the problem of the composition of matter became much easier .
Since the Englishman William Prout (1785-1850) and the German Jeremias Benjamin Richter (1762-1807) had developed and experimentally proven the laws of constant and equivalent mass proportions of substances (2 grams of sulfur react constantly with 2 grams of oxygen to form 4 grams of sulfur dioxide or constant with 3 grams of oxygen to 5 grams of sulfur trioxide), the time began when chemists all over the world began to set up all possible formulas for pure substances. This was made easier by the fact that the Swede Jöns Jakob Bezelius (1779–1848) developed a notation system with letters for the elementary substances. The chemical reactions mentioned so far in this text can be written as follows with its formula "equations" (the = sign must not be read as in mathematics!):
2 H2O = 2H2 + O2
S + O2 = SO2
2 S + 3 O2 = 2 SO3
The knowledge about pure substances became ever greater, a system of order became more and more urgent, because one wanted to summarize and interpret similar substances, which caused the similarity. Max Pettenkofer (1818–1901) in Germany, John Alexander Newlands (1838–1898) in England, Alexandre Chancourtois (1820–1866) in France had developed such systems of order; we can see them as the forerunners of the modern periodic tables.
The Russian Dimitri Mendeleev (1834–1907) was the first to compile a periodic table of the elements that even allowed predictions for undiscovered elements. Mendeleev bravely defied all sorts of inconsistencies and demanded even more courageously that there must be still undiscovered elements (germanium, gallium and scandium) because he found gaps in his system and he could also roughly say which properties the elementary substances and which formulas were more appropriate Connections of these elements would have. When fabrics were actually produced that pretty much matched his predictions from 1869, Mendeleev's fame was of course assured.
Independently of Mendeleev, the German Julius Lothar Meyer (1830–1895) also developed a very similar periodic table of the chemical elements, a table with 16 columns [Literature 79]. Both Mendeleev and Meyer were inspired to do this at the Karlsruhe Chemists' Congress in 1860 by the Italian Stanislao Cannizzaro (1826–1910), who in turn broke a lance for the atomistic theory of his teacher Amadeo Avogadro (1776–1856). The topic of this congress was the nomenclature of chemical compounds and their formulaic representation as well as the question of the atomic and molecular weights of chemical compounds. Both Mendeleev and Meyer developed their systems out of a didactic motivation: to give an overview of the abundance of all already identified and yet to be identified pure substances.
Mendeleev and Meyer disagreed on the even deeper question of whether the elementary substances themselves could not be traced back to a single primordial matter, a “protohyle”. Meyer adhered to the hypothesis developed by the Englishman William Prout that all matter is ultimately made up of highly condensed hydrogen, while Mendeleev contradicted it because of inconsistencies in the molar masses of atomic substances. Both Mendeleev and Meyer could not have known at that time that in the micro range of protons, neutrons and electrons the law of the conservation of mass due to the significant equivalence of mass and energy (DE = Dm × c²) can no longer be applied .
Prout’s hypothesis is closely related to the idea of the atomistic structure of matter. The idea that there are first building blocks for all substances ("atoms") comes from Democritus (around 460 to 370 BC). It has been discussed repeatedly since then. But only since the Englishman John Dalton (1766–1844) plausibly explained the constant and equivalent mass proportions of Prout and Richter with it, have chemists argued for a whole century whether atoms really exist. Dalton himself spoke of the “law of constant and multiple proportions. Mendeleev did not care whether there were atoms or not (he tended to view them as convenient thought models). The dispute only ended when so-called discrete phenomena (flashes of light or cloud chamber traces caused by radioactive preparations or the integer amplitudes of oscillating oil droplets found by the American Robert Andrews Millikan) could no longer be interpreted in any other way than by assuming that atoms were not after all indivisible, but "built up" from elementary particles (protons, electrons, neutrons).
This was where a new intensive occupation with the periodic table of the elements began and it was the Dane Niels Bohr (1885–1962) who, with his theory of the atomic structure, was the first to interpret the structure of the periodic table, which Mendeleev had already found in principle. Since then, the periodic table of the elements has not only been the common system of order for the abundance of substances, but also the law of formation for the individual types of atoms.
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