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Periodic Table

September 27, 2018 at 9:18 pmCategory:General

Periodic system of elements (Mendeleev) – classification of chemical elements, allowing them to reveal the dependence of various properties on the atomic mass (more precisely, the number of protons in an atomic nucleus). The system is designed Russian chemist Mendeleev in the years 1869-1871 based on open them in 1869, the periodic law and is its graphic expression. Filed under: NY Museums . Total invited several hundred variants of the image of the periodic system (Analytical curves, tables, geometric figures, etc.). In the modern version of the system is assumed mixing elements in the two-dimensional table in which each column (number of columns is 8) determines the basic physico-chemical properties, and the rows represent the periods, to some extent similar to each other. The original work was titled Mendeleev as "Experience of elements based on their atomic weight and chemical similarity. According to legend, the idea of such a system came to him in a dream, but we know that once asked how he discovered the periodic system, Mendeleev said: "I'm over it, maybe twenty years of thought, and you think: sitting and suddenly Done. Click NY Museums to learn more.

German L. Meyer in 1864 on the basis of data on atomic weights suggested a table showing the ratio of atomic weights for several characteristic groups of elements. Many, especially in Germany, and believe it discoverer of the system – in 1870 he published his table of elements, developed, apparently independently of Mendeleev. Not to be confused with copyright, most students of the Western world are studying this system simply as "periodic system of elements", without mentioning the name of the discoverer. The essence of the discovery is that with increasing atomic weight of the chemical element of its properties do not change monotonically, but periodically. After a certain number of different properties of elements arranged in increasing atomic weight, the properties begin to repeat.

For example, sodium, like potassium, neon like argon, while gold is similar to silver and copper. Of course, the properties are not repeated exactly, are added to them and change. Subsequently, it became clear that the periodicity of the system elements is determined not by atomic weight, and the nuclear charge or atomic number of which depends on the structure and the filling of electronic shells of an atom of the element (atomic orbitals). Periodic system of elements