The periodic table was first published in 1869 by Dmitri I. Mendeleev, who organized the then-known elements into a system based on their characteristics. Since then, it has evolved significantly as new elements have been discovered and our knowledge of their properties has expanded.
It is based on the principle that the chemical properties of elements repeat periodically with increasing atomic number. This means that elements in the same group, which are in the same vertical column of the table, have similar chemical properties.
Also, the arrangement of elements in horizontal rows represents increasing atomic number. The periodic table of chemical elements is an indispensable tool for every chemist and scientist involved in chemistry. It is an organized classification of all chemical elements known to science, providing information about their properties, structures, and behaviors.
It presents the chemical elements in order according to their atomic number, the number of protons, and is divided into series, which represent various classes of elements. These classes include metals, nonmetals, noble gases, metalloids, common metals, and many others.
It provides information about each chemical element, such as its symbol, name, atomic weight, atomic number, structure, properties and much more. We can find information about the physical state of the elements (solid, liquid or gas), their melting and boiling points, electronegativity, electron affinity, van der Waals radius, hardness, density, conductivity, thermal and electrical conductivity, heat of fusion, abundance in the universe and many other properties.
It also provides information about isotopes of elements. Isotopes are different forms of an element that differ in the number of neutrons they have. The periodic table shows the number of isotopes and provides information about their mass, excess mass, binding energy, abundance, and other important parameters.
It is used in many areas of chemistry and science in general. It is an essential tool for predicting and analyzing chemical reactions, the composition and properties of chemical compounds, understanding the structures and behaviors of elements, as well as for learning and teaching chemistry.
In this table, the elements are arranged in vertical columns called groups and in horizontal lines called periods appearing in ascending order of their atomic number.
The position and properties of each element were determined by the arrangement of electrons in the atoms (layers) of their atoms. Therefore the elements in the same column (of the table) have the same number of electrons in their outer layer in their atoms, and consequently have similar chemical properties.
While elements in the same row (period) have their electrons distributed over the same number of shells (in the ground state), they exhibit similar physical properties.
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