Investigating chemical bonds in crystal binding

Document Type : Original research

Authors

1 Department of Physics Education, Farhangian University, P.O. Box 14665-889, Tehran, Iran

2 Department of Physics, University of Tabriz

Abstract

The cohesive factor in solids is the electrostatic interaction of attraction between the negative charges of electrons and the positive charges of the nucleus. Solids are classified based on lattice symmetry and chemical bonds. On the other hand, based on the spatial distribution of electrons, chemical bonds can be classified into 5 categories: ionic bonds, covalent bonds, van der Waals or molecular bonds, hydrogen bonds, and metallic bonds. The coupling of two dipoles, one due to oscillations, and the other due to the electric field produced by the former, leads to an attracting force, which is called van der Waals force. The van der Waals bond is relatively weak. In contrast, ionic bonding results from the electrostatic interaction of oppositely charged ions. There is a strong attractive Coulomb interaction between nearest neighbor ions, which is responsible for ionic bonding. The ionic bond is very strong, and experimentally, this strength is characterized by a relatively high melting temperature. The covalent bond is another important bond that exists in many solids. A covalent bond between two atoms is usually formed by two electrons, one from each atom participating in the bond. Normally the covalent bond is strong. On the other hand, metals are characterized by their high electrical conductivity. Electrons that can move between crystals are called conduction electrons. The main characteristic of metallic bonding is the low energy of valence electrons in metals compared to free atoms. Some qualitative factors of this truth are explained in this article. Metallic bonding is weaker than ionic and covalent bonding. Due to the misunderstandings of school and university students, which is the result of their previous ideas in the field of chemistry and different types of interatomic bonds, the present article has tried to express the types of interatomic bonds in solids and compare the strength of each by calculating and drawing diagrams of cohesive energies.

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