Periodic Table

Periodic Table

The periodic table of the elements, also called the periodic table or PSE, shows all chemical elements with increasing nuclear charge and divided according to their chemical properties into periods as well as main and subgroups. a. the overview, earlier it was of particular importance for predicting the discovery of new elements and their properties.

Such chemical elements have been known since ancient times or antiquity. However, the dating of the discovery is only imprecise and can vary by several centuries depending on the literature source. More reliable dating is only possible from the 18th century, until then only 15 elements were known and described as such.

In the 19th century most of the elements were discovered and scientifically described. At the beginning of the 20th century only 10 of the natural elements were still unknown. Since then, v. a. difficult to access, mostly radioactive elements. Of these, many are not natural and are the product of artificial nuclear fusion processes. The two artificial elements darmstadtium (eka-platinum) and roentgenium (eka-gold) were only produced in December 1994.

At the beginning of the 19th century, Wolfgang Döbereiner first established a connection between the atomic mass and the chemical properties of individual elements. In 1863, John Alexander Reina Newlands presented a table of the elements in groups of eight, broken down by atomic mass.

The actual periodic table was set up in 1869 almost simultaneously and independently by Lothar Meyer and Dmitri Ivanovich. They also arranged the chemical elements according to increasing atomic masses. They arranged elements with similar properties one below the other. The structure of atoms was discovered in the 20th century, and the periodicity was explained by the structure of the electron shell.