Mendeleev standing on the shoulders of giants
Mendeleev was not the first scientist to create the Periodic Table of the Elements. Compared to others, his genius lies in the fact that space is left in the table. He realizes that certain elements are missing and have yet to be discovered.
In 1789, the French chemist Antoine Lavoisier published a list of 33 known chemical elements (partially simple and compounds), which were divided into four groups of gases, metals, non-metallic minerals and rare earths. It is the world’s first classification table for related elements.
In 1803, the British chemist and physicist John Dalton proposed atomic theory. He used a relatively comparative method to obtain the atomic weight of each element and published the first atomic scale, which triggered a sensation in the scientific community and worked on the determination of atomic weight. Value. Without reliable relative atomic mass, it is impossible to have a reliable molecular formula, and it is impossible to understand the chemical reaction, nor to have the periodic table of Mendeleev.
Subsequently, scientists such as Gyordo, Odrin, Meyer, Newlands, and Hinrichs all laid a valuable and solid foundation for the advent of the periodic table of chemical elements, allowing Mendeleev to extract the “inventive element cycle.” The laurel of the table became possible.
Mendeleev was born in 1834 and lived in Siberia before the age of 10. Under the guidance of an exile, he became interested in chemistry. In 1850, he entered the Peterborough Teachers College. After graduation, he worked as a secondary school teacher and later as an associate professor at the University of Petersburg. In 1867, Mendeleev, who was promoted to professor, systematically lectured on inorganic chemistry and began to write a chemistry textbook, “Chemical Principles.” In the process of writing, he encountered a problem, how to organize and unify the 63 elements known at the time in a logical way.
Mendeleev wanted to unfold a picture depicting the unity and logic of matter in front of the students, pointing out several important rules of the structure of the universe, but there was no such law at the time. As a result, he began to look for regularity or unity among the various elements of the maze.
On the basis of the element table drawn by the predecessors, Mendeleev struggled to explore the relationship between the exact atomic quantity and the elemental nature of the element, and finally made breakthrough progress, completing the leap from perceptual recognition of rational cognition. The writing of the book “Chemical Principles” in 1868 laid the foundation for his invention of the periodic table of elements. He conducted an “attempt to build an elemental system based on atomic weight and chemical similarity.” On February 17, 1869, Mendeleev published the first periodic table of elements, explicitly using the term “periodic”. In this periodic table of elements, the period is a vertical line and the family is a horizontal line.
In December 1871, Mendeleev published the second periodic table of elements. In this table, he is vertically arranged in horizontal rows, and the elements of the same family are in the same vertical line, which highlights the periodicity of the nature of the elements, which indicates the completion of the discovery of the chemical element cycle law. Then he organized the system into four papers. Until 1906, he published five periodic table of elements.
Mendeleev was not the first scientist to create the Periodic Table of the Elements. Compared to others, his genius is that he left room in the table. He realized that certain elements were missing and had to be Find. He pointed out that according to the atomic mass, the elements are arranged in order of small to large, and new elements are found where the atomic weight jumps too large, so the periodic law can predict the elements yet to be discovered. At the same time, he also accurately predicted the nature of the missing elements.
Mendeleev’s lofty honour for the “inventory periodic table” cannot be doubted. To commemorate Mendeleev, element 101 is named “钔” (Md, seventh cycle, element IIIB).
The highest state of science should be the embodiment of philosophical thinking. As Engels said: “Mendeleev unconsciously applied Hegel’s quantity into a qualitative law and completed a honour in the history of science. This honour can calculate the unknown planet and the Neptune orbit with Levier. The honours of the industry are in the same position.”
Whether the periodic table should be rearranged
Future science will not overturn the periodic table of elements. The discovery of the atomic structure not only did not overturn the scientific nature of the Mendeleev periodic table arrangement, but found that they were so strikingly consistent.
When Mendeleev invented the periodic table, rare gases have not yet been discovered. After 1895, inert rare gas elements were discovered one after another. Mendeleev respected the development of scientific practice. In the periodic table of elements proposed in 1906, they were arranged in front of the first group and were designated as the zero family. The complete new family has been formed, and the cycle system has been perfected. It has also formed a new cycle of understanding, which has led to the development of the cycle theory. The new findings and arrangements have not contradicted the periodic law of the elements and the periodic table.
From the end of the 19th century to the beginning of the 20th century, scientists discovered electrons, protons, neutrons, and nucleuses. In 1911, the British physicist Rutherford proposed that the mass of atoms is mainly concentrated on the nucleus (the number of protons and the number of neutrons are combined as atomic weight), and the number of charges in the nucleus is equal to the atomic number of the element, which greatly develops the gate. Dylev’s elemental cycle law and the elemental cycle theory is based on a more correct and scientific essence. Until 1921, the Danish physicist Boer et al. proposed some rules for the arrangement of electrons outside the nucleus, established the theory of modern atomic structure, and developed the periodic law of elements again.
The deepening of quantum chemistry research solves the description of the state of extranuclear electron motion and the arrangement of extranuclear electrons, thus truly revealing the essence of the periodic law of elements. The periodic variation of the elemental properties is due to the periodic variation of the atomic electronic layer structure, which profoundly and accurately reflects the atomic microstructure and makes the periodic law more perfect.
It can be seen that the development of the periodic table has gone through many tests. The discovery of the atomic structure not only did not overturn the correctness of the Mendeleev periodic table arrangement, but found that they were so strikingly consistent – so far, the discovery of new elements is in accordance with the laws of atomic physics and is within the scope of human prediction. within.
The periodic table reveals the essence of the elemental cycle law and its inclusiveness, especially the guidance for the continuous discovery and synthesis of new elements. It proves to the world time and time again that the periodic table does not need to be rearranged, and the future science will not Overthrow it.
Will synthetic elements expand the periodic table indefinitely?
The formation and development of the periodic table of chemical elements is an important milestone in the history of science. It is inseparable from the excellent research and continuous improvement of scientists from generation to generation. These great scientists are the light of human civilization.
Before 1940, uranium was always at the end of the cycle system. People use “transuranic elements” chemically to refer to heavy elements with atomic numbers above 92 (uranium). In 1944, the American nuclear chemist Siboge proposed the tethered theory based on the electronic structure of heavy elements. This theory has made the modern periodic table tend to be complete, and it has also pointed out the direction for the subsequent synthesis of artificial transuranic elements one by one.
According to the theory of electronic structure, humans have successively synthesized the super heavy elements from 104 to 118, thus perfecting the seventh cycle of the periodic table, which not only makes it possible for scientists to synthesize heavier and more practical elements in the future. The modern periodic table has perfected the “formal beauty that symmetry dominates.” This is the embodiment of the inner beauty of the material movement in nature, and the combination of the freedom to create beauty and the beauty of nature.
Following the successful synthesis of elements 104-118 and the recognition and naming of the International Union of Pure and Applied Chemistry (IUPAC), the Chinese names of four new elements were also announced in the near future, with an atomic number of 113 ( , Nh), 115 (镆, Mc), 117 (, Ts) and 118 (, Og).
The Stabilization Island Hypothesis encourages scientists to find new super-heavy elements in both natural and synthetic fields. This is a large-scale periodic table with fantasy. But scientific inquiry tells us that there may be an upper limit on the periodic table. This is because protons are positively charged, and strong interactions overcome the Coulomb repulsion between protons, binding protons and neutrons inside the nucleus. Strong interactions are short-range forces that are almost gone beyond a certain distance. The heavier the element, the easier it is to exceed this limit, so the element is extremely unstable. Therefore, the element cannot be increased indefinitely.
In addition, it is also necessary to consider whether the heavy element can be effectively observed. If the heavy element decays too fast to be observed, it cannot be proved.