The periodic table of chemical elements or, as it is also called, the Mendeleev table, which made it possible to classify chemical elements, depending on their properties and the charge of the atomic nucleus, was discovered by the Russian chemist D.I.Mendeleev in 1869.
According to legend, the system of chemical elements came to Mendeleev in a dream, but the author himself said that he had spent 20 years looking for a solution. The discovery of the periodic system was facilitated by Mendeleev's love for playing solitaire. The scientist indicated the atomic weights of certain elements on playing cards, and then laid them out as if he were playing a card game.
Initially, it consisted of 56 elements, however, with the development of fundamental and applied science (including nuclear fusion) in the 20th century, the number of currently discovered elements reached 118. The 113th, 115th, 117th and 118th elements were declared by IUPAC (International Union of Pure and Applied Chemistry) quite recently, on December 30, 2015.
The Latin alphabet has 26 letters, and almost all of them are used to name elements in the periodic table. Except for one - the letter "J".
In total, over the past 50 years, Mendeleev's Periodic Table has been replenished with 17 new elements (from 102 to 118), 9 of which were synthesized at the Joint Institute for Nuclear Research in Dubna near Moscow.
Most isotopes of superheavy elements (elements with atomic numbers> 100) are unstable and decay within a very short period of time. For example, the recently discovered ununpentium, also known as element 115 and eka-bismuth, has a half-life of only about 220 milliseconds.
One of the important features that makes the periodic table an outstanding discovery is its predictive power. At the time of its appearance, the table had empty cells for elements that, according to Mendeleev's assumptions, should exist, but had not yet been discovered. For example, Mendeleev described the properties of gallium, scandium and magnesium even before their discovery.
If we take a modern periodic table, cut out columns from its middle and fold them in half in groups of 4 elements, then the groups that touch (“kiss”), in the chemical sense, can “love each other, ” that is, interact. Elements from these groups will have complementary (i.e., complementary) structures, which makes possible reactions between them.
The largest periodic table was installed on the walls of the Faculty of Chemistry at the University of Murcia in Spain. In total, the installation occupies a total of about 150 m2 and consists of 118 metal squares measuring 75 × 75 cm.