A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or between atoms and other covalent bonds. A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny In short, attraction-to-repulsion stability that forms between atoms when they share electrons is known as covalent bonding.
Covalent bonding includes many kinds of interactions, including σ-bonding, π-bonding, metal-metal bonding, agostic interactions, and three-center two-electron bonds. In Chemistry, sigma bonds ( σ bonds) are the strongest type of covalent Chemical bond. In Chemistry, pi bonds ( π bonds) are covalent Chemical bonds where two lobes of one involved electron orbital overlap two lobes Agostic interaction is a term in Organometallic chemistry, for the interaction of a coordinately-unsaturated Transition metal with a C-H bond, when the A three-center two-electron bond is an electron deficient Chemical bond where three atoms share two electrons  The term covalent bond dates from 1939.  The prefix co- means jointly, associated in action, partnered to a lesser degree, etc. ; thus a "co-valent bond", essentially, means that the atoms share "valence", such as is discussed in valence bond theory. In Chemistry, valence, also known as valency or valency number, is a measure of the number of Chemical bonds formed by the Atoms In Chemistry, valence bond theory explains the nature of a Chemical bond in a Molecule in terms of atomic valencies. In the molecule H2, the hydrogen atoms share the two electrons via covalent bonding. Covalency is greatest between atoms of similar electronegativities. " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons Thus, covalent bonding does not necessarily require the two atoms be of the same elements, only that they be of comparable electronegativity. Because covalent bonding entails sharing of electrons, it is necessarily delocalized. In chemistry delocalized electrons are Electrons in a Molecule that are not associated with a single Atom or to a Covalent bond. Furthermore, in contrast to electrostatic interactions ("ionic bonds") the strength of covalent bond depends on the angular relation between atoms in polyatomic molecules. An ionic bond (or electrovalent bond) is a type of Chemical bond that can often form between Metal and Non-metal Ions (or
|“||(p. Irving Langmuir ( January 31, 1881 in Brooklyn New York – August 16, 1957 in Woods Hole Massachusetts) was an 926)… we shall denote by the term covalence the number of pairs of electrons which a given atom shares with its neighbors.||”|
The idea of covalent bonding can be traced several years prior to 1920 to Gilbert N. Lewis, who in 1916 described the sharing of electron pairs between atoms. Gilbert Newton Lewis ( October 23, 1875 - March 23, 1946) was a famous American physical chemist known for the discovery He introduced the so called Lewis notation or electron dot notation or The Lewis Dot Structure in which valence electrons (those in the outer shell) are represented as dots around the atomic symbols. Lewis structures, also called Lewis-dot diagrams are diagrams that show the bonding between Atoms of a Pairs of electrons located between atoms represent covalent bonds. Multiple pairs represent multiple bonds, such as double and triple bonds. Some examples of Electron Dot Notation are shown in the following figure. An alternative form, in which bond-forming electron pairs are represented as solid lines, is shown alongside.
While the idea of shared electron pairs provides an effective qualitative picture of covalent bonding, quantum mechanics is needed to understand the nature of these bonds and predict the structures and properties of simple molecules. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Walter Heitler and Fritz London are credited with the first successful quantum mechanical explanation of a chemical bond, specifically that of molecular hydrogen, in 1927. Walter Heinrich Heitler ( 2 January 1904 &ndash 15 November 1981) was a German physicist who made contributions to Quantum electrodynamics Fritz Wolfgang London ( March 7, 1900 &ndash March 30, 1954) was a German -born American theoretical Physicist. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1  Their work was based on the valence bond model, which assumes that a chemical bond is formed when there is good overlap between the atomic orbitals of participating atoms. An atomic orbital is a Mathematical function that describes the wave-like behavior of an electron in an atom These atomic orbitals are known to have specific angular relationships between each other, and thus the valence bond model can successfully predict the bond angles observed in simple molecules.
Bond order is a number that indicates the number of pairs of electrons shared between atoms forming a covalent bond. Bond order is the number of bonds between a pair of atoms For example in Nitrogen N≡N the bond order is 3 in Acetylene H−C≡C−H the bond order between the The term is only applicable to diatomic molecules, but is used to describe bonds within polyatomic compounds as well. Diatomic molecules are molecules made only of two Atoms of either the same or different Chemical elements The prefix di- means two in Greek
Most bonding of course, is not localized, so the above classification, while powerful and pervasive, is of limited validity. Three-center bonds do not conform readily to the above conventions. A three-center two-electron bond is an electron deficient Chemical bond where three atoms share two electrons
Many bonding situations can be described with more than one valid Lewis Dot Structure (for example, ozone, O3). OZONE is an object oriented Operating system written in the C programming language. In an LDS diagram of O3, the center atom will have a single bond with one atom and a double bond with the other. The LDS diagram cannot tell us which atom has the double bond; the first and second adjoining atoms have equal chances of having the double bond. These two possible structures are called resonance structures. Resonance in Chemistry is a theory used to represent and model certain types of non-classical Molecular structures Resonance is a key component In reality, the structure of ozone is a resonance hybrid between its two possible resonance structures. Instead of having one double bond and one single bond, there are actually two 1. 5 bonds with approximately three electrons in each at all times.
A special resonance case is exhibited in aromatic rings of atoms (for example, benzene). Benzene, or benzol, is an organic Chemical compound and a known Carcinogen with the molecular formula C 6 H 6 Aromatic rings are composed of atoms arranged in a circle (held together by covalent bonds) that may alternate between single and double bonds according to their LDS. In actuality, the electrons tend to be disambiguously and evenly spaced within the ring. Electron sharing in aromatic structures is often represented with a ring inside the circle of atoms.
Lewis Dot Structures for molecules with resonance are shown by creating the dot structure for every possible form, placing brackets around each structure,and connecting the boxes with double-headed arrows.
Today the valence bond model has been supplanted by the molecular orbital model. In Chemistry, a molecular orbital (or MO) is a region in which an Electron may be found in a Molecule. In this model, as atoms are brought together, the atomic orbitals interact to form molecular orbitals, which are linear sums and differences of the atomic orbitals. These molecular orbitals are a cross between the original atomic orbitals and generally extend between the two bonding atoms.
Using quantum mechanics it is possible to calculate the electronic structure, energy levels, bond angles, bond distances, dipole moments, and electromagnetic spectra of simple molecules with a high degree of accuracy. Bond distances and angles can be calculated as accurately as they can be measured (distances to a few pm and bond angles to a few degrees). For small molecules, calculations are sufficiently accurate to be useful for determining thermodynamic heats of formation and kinetic activation energy barriers.