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Introduction to Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
The chemical bond is the attractive force between the atoms in a molecule that binds together the atoms. It originates from the tendency of atoms to acquire the stable inert gas configuration. The main types of bonds are as follows: (i) ionic or electrovalent bond in which electrons are transferred from one atom to another forming positive and negative ions that stick together by electrostatic force; (ii) covalent bond in which the atoms are held together by sharing electron pairs; bonds formed by sharing one, two, or three pairs of electrons are called single, double, or triple bonds respectively; (iii) hydrogen bond, in which a hydrogen atom attached to one of the three elements, fluorine, oxygen, or nitrogen, is able to form a bridge with another one of these three elements; and (iv) metallic bond, forming in metals, which, due to their low ionization energies, lose one or more of their outer shell electrons, becoming positive ions so that the metal is pictured as a sea of free mobile electrons in which positive ions are immersed. The free electrons are said to be delocalized. Delocalization is the spreading of a molecule’s electrons over the molecule.
Orbitals and Bonding
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
Bond dipole moment is a measure of the polarity of a chemical bond, generally induced by differences in electronegativity of the two atoms in that bond. The bond dipole symbol is μ and the unit of measurement is the Debye (D). Is the C—H bond considered to be polarized?
Bonding and Properties of Materials
Published in Ashutosh Kumar Dubey, Amartya Mukhopadhyay, Bikramjit Basu, Interdisciplinary Engineering Sciences, 2020
Ashutosh Kumar Dubey, Amartya Mukhopadhyay, Bikramjit Basu
The physical, mechanical, electrical, and thermal properties of materials are decided by the nature of the bond, which combines atoms into molecules/crystals. The concept of molecules/crystals can be considered to be originated from the tendency of atoms to attain the inert gas configuration. This tendency of atoms binds them together to form a stable configuration/structure. The force that holds the atoms together is, in general, referred to as the chemical bond. The formation of molecules/crystals can be represented as the possible lowest energy form of their free entities. In view of the fact that the bonding plays an important role in understanding the properties of materials, this chapter discusses the fundamental aspects of chemical bonding and its correlation with the various properties of materials.
An intrinsic criterion of defining ionic or covalent character of AB-type crystals based on the turning boundary radii calculated by an ab initio method
Published in Molecular Physics, 2018
Dong-Xia Zhao, Chun-Yu Yan, Zun-Wei Zhu, Le Zhang, Yi-Ming Jiang, Rui Gong, Zhong-Zhi Yang
Properties of a substance are dependent on its composition and its molecular and/or atomic arrangement. The bonding character and network between ions or atoms in a molecule or a solid are essentially and directly determine its structure, the atomic or ionic arrangement, and its properties. Exploration and understanding of the bonding nature in molecules and solids have been one of the most important topics ever since quantum theory of molecules was established [1–14]. The chemical bonds are usually divided into three extreme types, namely covalent, ionic and metallic, depending on their respective electronic nature. Although there is no sharp boundary between the ionic bonding and covalent bonding from quantum mechanical point of view, yet it is convenient and effective to consider each of these as a separate entity in discussing and interpreting various properties of a molecule or a crystal [1,2].
Evolution in the surface modification of textiles: a review
Published in Textile Progress, 2018
Ayoub Nadi, Aicha Boukhriss, Aziz Bentis, Ezzoubeir Jabrane, Said Gmouh
Covalent chemical bonds involve the sharing of a pair of valence electrons by two atoms. The idea of immobilizing a dye molecule by covalent bond formation with reactive groups in a fibre originated in the early 1900s, but it was not until 1955 that Rattee and Stephen, working for ICI in England, developed a procedure for dyeing cotton with fibre-reactive dyes containing dichlorotriazine groups [10, 11]. Reactive dyes for cotton are the only textile colourants designed to form a covalent bond with the substrate during the application process. Reactive dyes are the most permanent of all dye types. These dyes react with cellulose either by the addition or substitution mechanism. For example, vinyl sulfonic derivatives dyes react with cellulose by the nucleophilic addition to a carbon carbon double bond as illustrated by reaction (1) [9, 10] where Cell–OH is the cellulose with a reactive hydroxyl group, Dye–SO2–CH = CH2 is the dye with its reactive vinyl sulfonic atom, and dye –SO2–CH = CH–O–Cell the dye linked to the cellulose by a covalent bond.