covalent bond

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covalent bond

(kō'vā`lənt): see chemical bondchemical bond,
mechanism whereby atoms combine to form molecules. There is a chemical bond between two atoms or groups of atoms when the forces acting between them are strong enough to lead to the formation of an aggregate with sufficient stability to be regarded as an
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Covalent Bond


a chemical bond between two atoms that is formed by a shared electron pair (one electron from each atom). Covalent bonds exist both in molecules (in all states of aggregation) and between the atoms that form crystal lattices. They may unite like atoms (in H2 and C12 molecules and diamond crystals) or unlike atoms (in water molecules and crystals of carborundum, SiC).

Almost all the main bonds in the molecules of organic compounds are covalent (C—C, C—H, C—N, and so on). Covalent bonds are very strong, which explains the low chemical activity of paraffin hydrocarbons. Many inorganic compounds whose crystals have an atomic lattice (that is, are formed by a covalent bond) are refractory and characterized by great hardness and wear resistance; among them are certain carbides, suicides, borides, and nitrides (particularly borazone, BN), which are widely used in modern technology.


covalent bond

[kō′vā·lənt ′bänd]
A bond in which each atom of a bound pair contributes one electron to form a pair of electrons. Also known as electron pair bond.
References in periodicals archive ?
It is likely that immobilization by covalent bonding caused conformational changes in the three-dimensional structure of the enzyme, which hindered substrate access to the immobilized enzyme active site, consequently reducing the maximum reaction speed when compared with the free lipase (Hiol et al., 2000; Yang et al., 2010).
Emilio Sanchez, spokesman for ForeignTRADEX serving New Mexico, Arizona, Texas and Colorado regions said the website can be used to find direct and indirect suppliers of most types of chemicals such as element of compound based chemicals, including metal, nonmetal, metallic, covalent bonding, molecular, ionic and element formulas as well as various chemical supplies at
Specific topics include the synthesis and characterization of new fluorinated polymides, imidization of polyester-amine salt precursors to polymides, liquid crystalline structures and crystallization morphology in aromatic bismides and their blends with semicrystalline polymide, Ceramide materials for advanced high-performance and high-temperature applications, polymide matrices for carbon-to-carbon composites with turbostatic structures, molecular assembly of polymides and oligoimides with direct covalent bonding, and electroless metallization of polymides.
Atomic structure, valence electrons, and covalent bonding
We also found that covalent bonding of the treatment chemical to silica is preferred to just associative, i.e., hydrogen bonding.
The first volume focuses on fundamental aspects of chemical bonding, and presents such perspectives as the physical origin of covalent bonding, the natural bond orbital (NBO) view, the valence bond perspective, the conceptual density functional theory, and relativity and chemical bonding.
Although these IR spectra themselves do not provide direct evidence for any covalent bonding between the PNIPA hydrogel and modified silica, the results indicating the presence of ester carbonyl groups in the absence of any double bonds in the PNIPA/modified silica hydrogel suggested that the double bonds introduced on the modified silica were copolymerized with NIPA and that the modified silica was bound with PNIPA hydrogel via covalent bonding.
To estimate the extent of covalent bonding between the polymer and inorganic particles, the nanocomposite samples were extracted with THF for 7 days using a Sohxlet extractor.
4 indicates that alternating copolymer poly(styrene-maleic anhydride) (SMA) is successfully grafted onto the surface of the silica nanoparticles through covalent bonding. The absorption band at 1720 c[m.sup.-1] in the IR spectrum is a characteristic band of [v.sub.> c=o].
The adhesion enhancement of the Cu/pp-GMA-HDPE assemblies in the presence of Ar plasma pre-activation of the HDPE substrate was attributed to the covalent bonding of the plasma-polymerized GMA (pp-GMA) layer with the HDPE surface, the preservation of the epoxide functional groups in the pp-GMA layer, and the spatial interactions of pp-GMA chains with the evaporated Cu matrix.