Periodic Table of Elements
This Periodic Table arranges chemical elements such as hydrogen, silicon, iron and uranium according to their repetitive nature. The number of each element corresponds to the number of protons in its nucleus (the same number of electrons orbiting the nucleus). The modern periodic table provides a useful framework for analyzing chemical reactions and has been widely used in chemistry, physics, and other scientific fields.
The seven rows (called periods) of the table usually have metals on the left and nonmetals on the right. These columns are called groups and contain elements with similar chemical behavior. Six groups have accepted names and assigned numbers: for example, the elements in group 17 are halogens; group 18 are rare gases. Four simple rectangular regions or blocks related to filling different atomic orbitals are also shown. The organization of the periodic table can be used to derive the relationship between the properties of various elements and predict the chemical properties and behavior of undiscovered or newly synthesized elements.
The Russian chemist Dmitri Mendeleev published a periodic table of the elements in 1869. He developed the periodic table mainly to illustrate the repetitive trend between the properties of the known elements at that time. He was the first to predict certain attributes of unrecognized elements, which are expected to fill the gaps in the table. Facts proved that most of his predictions were correct. Finally, gallium and germanium were discovered in 1875 and 1886, which confirmed his predictions. With the discovery or synthesis of further new elements and the development of new theoretical models to explain chemical behavior, Mendeleev's ideas have gradually been expanded and improved.
The table presented below shows a widely used layout.