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This article comes from the official account of Wechat: back to Park (ID:fanpu2019), written by John D. Barrow, translated by Tang Jing and Li Pan

Faced with more than 60 known elements, all chemists tried to sort out a system, but only one succeeded: he made a table with many blanks, like a Sudoku waiting to be solved.

He never claimed to understand the structure and periodicity of the table.

This article is an authorized excerpt from the Gallery of Science (people's Post and Telecommunications Publishing House) with the title added by the editor.

People use the periodic table when studying chemistry. There is no doubt that if one day human beings are connected with life beyond Earth, the common ground of the two intelligent civilizations must contain an orderly and well-known list of elements.

John Emsley (John Emsley) [1]

Under the guidance of Aristotle, ancient Greek philosophers believed that the matter that existed in various forms and made up the world around us could be summarized by four basic substances, namely, earth, fire, air and water. Until the 17th century, this austere idea was respected as a fact, until chemistry derived from alchemy led to the discovery of other elements. "Earth" is not a single substance, and "Qi" is not just made up of a gas. In the 18th century, the elemental pedigree experienced a dramatic growth. At that time, many new metals were discovered, such as cobalt, nickel, manganese, tungsten, chromium, magnesium, uranium, as well as new gases, such as hydrogen, nitrogen, oxygen and chlorine, which were separated for the first time.

The concept of "element" in chemistry was first put forward by Robert Boyle: the substance that can no longer be decomposed by physical processes is the element. Since then, the French chemist Antoine-Laurent de Lavissier (Antoine-Laurent de Lavoisier) officially named the element [3] in 1789. Lavissier selected 33 substances, defined their elemental states, and divided them into four groups: metals, nonmetals, earth and gases. Later, it was found that some of these elements were actually compounds, while others, such as heat and light, were not even chemicals. The following is Lavissier's list of elements, and only those elements marked in red are still considered chemical elements today.

Gas: heat, light, hydrogen, nitrogen, oxygen.

Soil: alumina, barite, lime, magnesia, silica.

Metals: antimony, arsenic, bismuth, cobalt, copper, gold, iron, lead, manganese, mercury, molybdenum, nickel, platinum, silver, tin, tungsten, zinc.

Non-metals: sulfur, phosphorus, carbon, chloride, fluoride, borate.

The "earth" groups here are actually oxides, such as lime is calcium oxide and silica is silica, but under the conditions at that time, Lavasier could not extract oxygen atoms from the compounds and recognize the relevant elements independently. Other fake elements were in the "non-metallic" group, and similarly, Lavasier could not separate these elements into individual elements such as chlorine, fluorine and boron with the technology of the time. Lavissier became the enemy of Jean-Paul Mara during the French Revolution and was eventually guillotined during the "reign of terror" in 1794 because of his involvement in a national tax scandal. The judge declared: "the Republic does not need genius." But just 18 months later, the revolutionary government changed its tune and said that Lavasil had been wronged.

Later, a science teacher from Manchester, England, went a step further on the basis of this research. In 1805, John John Dalton submitted a paper to the Manchester Society of Literature and philosophy explaining the various ways in which elements are combined and how the basic components form different weights. At that time, most chemists thought that atoms were too small to study. But Dalton was more adventurous. He proposed a table of 20 elements and their weights, and marked symbols that showed how they were combined. Matter is represented by pictures and shows the patterns of its basic elements. From this list of elements, more compounds can be derived: compound 21 is water, described as HO; compound 22 is ammonia, and described as NH. These forms of expression are the embryonic state of the well-known chemical equation.

However, Dalton's symbols are too complex to use. The chemical symbol we use today comes from the Swiss chemist J ö ns Berzelius, who is also an admirer of Dalton [5]. Bezelius simply marks the element with the initials of its name (sometimes Latin or sometimes Arabic, such as potassium), or two letters when ambiguous, such as C for carbon and Co for cobalt. Bundling these symbols together, you can represent compounds, such as H2O. After 1835, this representation was adopted on a large scale and eventually used in equations that represent chemical reactions, such as [6]:

CuSO4 + 2HCl → H2SO4 + CuCl2

Dalton was shocked by the new complexity of chemical language. After reading the new plan, he said, "I'm afraid a young chemistry student will have to learn Hebrew." New elements continue to be discovered, and Humphrey Humphry Davy uses electrolysis to decompose the "earthy group elements" originally proposed by Lavasil into real elements. There were more than 60 elements in 1863. Is there a limit to the element "Big Bang"?

John Dalton's division of 20 elements and their weight in 1805 was indeed an attractive question at the time. If there is a limit, what is the number of elements? What factors can really determine this limit?

In the 19th century, many people bravely tried to classify elements in terms of weight, attributes, and so on. At that time, all the best chemists [7] established a similar system [8]. But without exception, they were defeated by a Russian chemistry professor from Siberia.

Dmitri Ivanovich Mendeleev (Dmitri Ivanovich Mendeleev) was born in 1822 at the home of the principal of a local primary school in Topolsk, Siberia. He has 13 brothers and sisters. Mendeleev's mother firmly believed that the son had special talents and should receive all possible quality education, so she sent her son to St. Petersburg to study. She's right. During his time in college, Mendeleev always ranked among the best in his studies. After that, he went to work in France and then to Heidelberg, Germany, where he worked as an assistant to the booming German chemist Robert Bunsen. Finally, in 1867, Mendeleev returned to St. Petersburg as a professor of chemistry at the university.

One day in the spring of 1867, Mendeleev stayed at home because of bad weather, so he had to take the opportunity to continue to write a new textbook called the principles of Chemistry. He doesn't know how to display and arrange the surging number of elements and their attributes. So he wrote the name of each element on a card, along with some attributes of the corresponding element, as well as oxides and hydrides. Then he began to arrange the cards in various ways, trying to find a pattern: horizontal arrangement of elements with the same valence, and vertical arrangement of elements in descending order of atomic weight. Suddenly, he found a very distinctive arrangement. He wrote down the results on the back of an old envelope, which can still be seen in St. Petersburg today.

In 1867, Mendeleev sketched the original periodic table, and then Mendeleev invented a more concise version. He arranged the first seven elements from lithium to fluorine horizontally in the order of increasing atomic weight [11], and then the seven elements from sodium to chlorine in the same way. As a result, periodicity occurs: in the column, two elements with similar chemical properties are next to each other. In the seven columns, the principal valence of the first column is 1, and that of the next column is 2, and then 3, 4, 3, 1, respectively. Next, Mendeleev soon discovered that if you flip the table and swap rows and columns, the table will be clearer. We can now recognize this result, even though today's table has been filled with many new elements.

Table 1 of elements has 8 columns, or 8 cycles. In a major improvement in 1870, Mendeleev assigned 63 known elements to 12 rows, starting with hydrogen and ending with uranium, each of which was placed in a column with similar chemical properties and arranged in ascending order of atomic weight.

The results shown in Mendeleev's table have an intuitive significant contribution to predicting the existence of new elements. He didn't put all the known elements in a complete periodic table, as others did. If it had been Aristotle, he would have done it. Mendeleev believes that if the periodic table has a logical structure, it means that there may be gaps in the table. He speculates that the new elements will fill these gaps, and the periodicity of the table can be used to predict atomic weight and atomic density. Under boron, aluminum and silicon, he inferred three "undiscovered" elements and named them boron-like, aluminum-like and silicon-like [12]. These three elements were later discovered one after another, and their atomic weights and densities were consistent with Mendeleev's predictions: "aluminum-like" was discovered in Paris, France, in 1875, called gallium (gallium, Latin for France); "boron-like" was discovered in Uppsala, Sweden, in 1879, called scandium (scandium, Latin for Scandinavia). "Silicon-like" was discovered in Freiberg, Germany, in 1886 and is called germanium (germanium, Latin for Germany).

Mendeleev also predicted that the new member of the fourth group (titanium) would have an atomic weight of about 180. This element was finally discovered in 1923 at the University of Copenhagen in Denmark. It has an atomic weight of 178.5 and is named hafnium (hafnium, Latin for Copenhagen).

In 1893, Mendeleev became director of the Russian Bureau of Metrology and made admirable contributions. He formally defined the composition of vodka: one molecule of wine and two molecules of water. The molecular weight shows that the vodka is composed of 38% alcohol and 62% water. In 1894, the Russian Bureau of Metrology issued a legal standard that slightly adjusted this figure to 40% alcohol and 60% water. This is 80% of the American standard alcohol (proof, that is, 1 alcohol is equal to 2 times the volume of alcohol).

With regard to Mendeleev's achievements and his great impact on contemporary scientists, Gerald Holden (Gerald Holton) once had such an analogy: "it's like a librarian putting all the books in a pile, weighing them one by one, and placing them on different shelves in ascending order of weight. Then he suddenly found that the first book on every shelf was about art, the second was about philosophy, the third was about science, the fourth was about economics, and so on. Our librarian may not understand the underlying principles of these rules, but once he finds that the order of the books on one of the shelves is "Art-Science-economy", he will leave a gap between art books and science books. and began to look for the lost weight of the philosophy book. " [13]

We can see the periodicity of the element table from an attribute of the element, such as dividing the atomic volume by the atomic weight. This was first discovered by Julius Julius Meyer in 1870 [14]. Alkali metals appear at the top of the chart.

Mendeleev never claimed to understand the structure and cyclical meaning of the watch. This is a great intuitive leap. He believed that these elements had an inherent symmetrical structure, but did not think that his form was still a convenient retrieval tool, which eventually led him to make dramatic discoveries and predictions. Although Mendeleev could not find the pattern of the elements in front of him, he knew that the table would help others to do it.

The modern version of the periodic table [15] is divided into seven rows (cycles), with 2, 8, 8, 18, 18, 32 and 32 elements in each row. After people discovered the quantum theory of atoms, this model can be understood. The nature of the quantum wave direction of electrons means that only integral times of wavelengths can allow electrons to be "loaded" in their surrounding orbits. The increase in the number of elements in each row of the periodic table reflects an increase in the number of electrons in the orbitals around the nucleus of each atom. Quantum mechanics allows the innermost orbitals (called shells) to contain two electrons, followed by six, then 10 and 14.

In the resulting periodic table, the number of elements in each row is the number of electrons when the orbit is full of electrons, so there are 8 = 2 + 6, 18 = 2 + 6 + 10, 32 = 2 + 6 + 10 + 14. The elements in each row are arranged according to the ascending order of the atomic number, while in each column, the elements are arranged according to the same number of outermost electrons, thus obtaining the modern form of the periodic table. In each line, we regularly add electrons to the orbit until we are full, and we end up with the inert (that is, inactive) gas on the far right of the periodic table. Then we open the next line and load the next level of track. It is worth mentioning that Mendeleev found this pattern before electrons and protons were discovered. He studied the atomic weight (determined by the number of protons in the nucleus of the element) and the valence (determined by the integrity of the electrons in the orbit) and used this simple method to find the nature of these two chemical properties.

Today, Mendeleev's periodic table appears on the walls of every chemical laboratory in the world [16]. It seems that his mother made the right decision at that time.

Mendeleev's periodic table. This is the first edition of the periodic table of elements by Russian chemist Mendeleev, which was printed in 1869. He left a blank for the new element in the table. Scientists later discovered these elements, which proved Mendeleev's conjecture. The elements listed in this version are represented by chemical symbols, sorted by atomic weight, but the complete ordering of elements has not yet appeared. In the final edition of 1871, the arrangement of atoms was the column or group as we know it today. Annotation

[1] EMSLEY J. Nature's Building Blocks. Oxford: Oxford UP, 2003: 527.

[2] LAVOISIER A. Trait é l é mentaire de chimie. 1789. This is a promotional textbook for new chemistry and has played an important role in chemistry education for many years.

[3] this is reminiscent of the modern definition of elementary particles. Of course, Lavissier does not know the internal structure of the atom: protons and neutrons made up of quarks make up the nucleus, which is surrounded by electrons.

[4] BERZELIUS J J. Essay on the Cause of Chemical Proportions, and on Some Circumstances Relating to Them: Together with a Short and Easy Method of Expressing Them. Annals of Philosophy. 181 (32): 443-454. Annals of Philosophy. 18 (143): 51-52,93-106,244-255,353-364. Reproduced in D. M. Knight (ed.). Classical Scientific Papers. New York: American Elsevier, 1968.

[5] in London in 1804, Bezelius learned about Dalton's research by listening to and discussing a speech given by Dalton at the Royal Academy of Sciences.

[6] the equation shows that copper sulfate (CuSO4) is combined with hydrochloric acid (HCl) to produce sulfuric acid (H2SO4) and copper chloride (CuCl2).

[7] among them, Julius Meyer's research is perhaps the most noteworthy. In 1868, he plotted the atomic volume and atomic weight of 49 elements and discovered periodic changes. He prepared a paper for his friend to comment on, but unfortunately, the friend was slow to respond and failed to finish it. As a result, Mendeleev published a more comprehensive version before Mayer.

[8] in 1815, the British chemist William William Prout designed a detailed list in which all elements were made of hydrogen. In the 19th century, it was called the Prout hypothesis.

[9] POSIN D Q. Mendeleyev: The Story of a Great Scientist. New York: McGraw-Hill, 1948.

[10] it can be seen in the Mendeleev Museum and Archives of St. Petersburg State University.

[11] hydrogen has been excluded because of its unique properties, while rare gases (such as helium) have not yet been discovered.

[12] in Greek, the prefix eka means "to follow".

[13] HOLTON G. Introduction to Concepts and Theories in Physical Science. 2nd rev. Ed with S. Brush. Princeton: Princeton UP, 1985: 337.

[14] the atomic volume of solid and liquid matter is equal to atomic weight divided by density.

[15] Don't forget that there may still be undiscovered overweight elements that are unstable and only exist for a short period of time.

[16] Primo Levy's masterpiece the Periodic Table of elements (LEVI P. The Periodic Table. London: Michael Joseph, 1985) tells the story of many unique experiences in the author's own extraordinary life, both as an industrial chemist and as a survivor of Nazi concentration camps. Different chapters describe different events and people, and each chapter is named after an element. For example, a famous Italian astrophysicist, the late Nicole Daraporta, appeared as a young teaching assistant in a chapter called "potassium", which tells the story of Trieste in 1941. In the 1980s, I met Daraborta in Trieste. He and my mentor, Denis Dennis Sciama, are both co-directors of the Italian Institute for Advanced International Studies (SISSA). So I had the privilege of personally confirming that Darapolta was as charming and friendly as the young man Levy knew 40 years ago. I even found that Dalaporta was nicknamed "potassium" by some Italians precisely because he played an important role in Levi's masterpiece. Levy once said that a careful study of the periodic table was an important psychological comfort to him when he was imprisoned and tortured during the war. He knows that when violators confuse black and white and try to tamper with human ethical standards, they cannot change the facts in the periodic table-there is a cornerstone of absolute truth that no one can shake.

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