Covalent bonding 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. In short, attraction-to-repulsion stability that forms between atoms when they share electrons is known as covalent bonding. Look up covalent in Wiktionary, the free dictionary. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ... For other uses, see Electron (disambiguation). ... Properties For other meanings of Atom, see Atom (disambiguation). ...

Covalent bonding includes many kinds of interactions, including σ-bonding, π-bonding, metal-metal bonding, agostic interactions, and three-center two-electron bonds.^[1][2] The term covalent bond dates from 1939.^[3] 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 the molecule H₂, the hydrogen atoms share the two electrons via covalent bonding. Covalency is greatest between atoms of similar electronegativities. 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. Furthermore, in contrast to electrostatic interactions ("ionic bonds") the strength of covalent bond depends on the angular relation between atoms in polyatomic molecules. Electron atomic and molecular orbitals, showing among others the sigma bond of two s-orbitals and a sigma bond of two p-orbitals In chemistry, sigma bonds (σ bonds) are a type of covalent chemical bond. ... Electron atomic and molecular orbitals, showing a Pi-bond at the bottom right of the picture. ... Agostic complexes are coordination compounds where the σ bond of a ligand serves as the electron pair donor. ... A three-center two-electron bond is an electron deficient chemical bond where three atoms share two electrons. ... In chemistry, valence, also known as valency or valency number, is a measure of the number of chemical bonds formed by the atoms of a given element. ... In chemistry, valence bond theory explains the nature of a chemical bond in a molecule in terms of atomic valencies. ... Electronegativity is a measure of the ability of an atom or molecule to attract electrons in the context of a chemical bond. ... In chemistry, delocalized electrons are electrons in a molecule that do not belong to a single atom or a covalent bond. ... Sodium and chlorine bonding ionically to form sodium chloride. ...

Schemes depicting covalent (left) and polar covalent (right) bonding in a diatomic molecule. The arrows represent electrons provided by the participating atoms.

Image File history File links Download high-resolution version (1692x898, 27 KB) I, Smokefoot, drew and release this. ... Image File history File links Download high-resolution version (1692x898, 27 KB) I, Smokefoot, drew and release this. ...

History

The term "covalence" in regard to bonding was first used in 1919 by Irving Langmuir in a Journal of American Chemical Society article entitled The Arrangement of Electrons in Atoms and Molecules:^[4] Irving Langmuir (January 31, 1881 in Brooklyn, New York - August 16, 1957 in Woods Hole, Massachusetts) was an American chemist and physicist. ...

The idea of covalent bonding can be traced several years prior to 1919 to Gilbert N. Lewis, who in 1916 described the sharing of electron pairs between atoms. 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. 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. Lewis in the Berkeley Lab Gilbert Newton Lewis (October 23, 1875-March 23, 1946) was a famous American physical chemist. ... G. N. Lewis Lewis structures, also called electron-dot structures or electron-dot diagrams, are diagrams that show the bonding between atoms of a molecule, and the lone pairs of electrons that may exist in the molecule [1] [2]. A Lewis structure can be drawn for any covalently-bonded molecule...

Early concepts in covalent bonding arose from this kind of image of the molecule of methane. Covalent bonding is implied in the Lewis structure that indicates sharing of electrons between atoms.

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. 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.^[5]. 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. 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. Image File history File links Covalent. ... Image File history File links Covalent. ... Methane is a chemical compound with the molecular formula . ... G. N. Lewis Lewis structures, also called electron-dot structures or electron-dot diagrams, are diagrams that show the bonding between atoms of a molecule, and the lone pairs of electrons that may exist in the molecule [1] [2]. A Lewis structure can be drawn for any covalently-bonded molecule... For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... Walter Heinrich Heitler (02. ... Fritz Wolfgang London (March 7, 1900–March 30, 1954) was a German-born American physicist for whom the London force is named. ... Molecular hydrogen, H2, is a molecule formed from two atoms of hydrogen. ... An atomic orbital is the description of the behavior of an electron in an atom according to quantum mechanics. ...

Bond order

Bond order is a number that indicates the number of pairs of electrons shared between atoms forming a covalent bond. The term is only applicable to diatomic molecules, but is used to describe bonds within polyatomic compounds as well. Bond order is the number of bonds between a pair of atoms. ... A computer rendering of the Nitrogen Molecule, which is a diatomic molecule. ...

1. The most common type of covalent bond is the single bond, the sharing of only one pair of electrons between two atoms. It usually consists of one sigma bond. All bonds with more than one shared pair are called multiple bonds.
2. Sharing two pairs is called a double bond. An example is in ethylene (between the carbon atoms). It usually consists of one sigma bond and one pi bond.
3. Sharing three pairs is called a triple bond. An example is in hydrogen cyanide (between C and N). It usually consists of one sigma bond and two pi-bonds.
4. Quadruple bonds are found in the transition metals. Molybdenum and rhenium are the elements most commonly observed with this bonding configuration. An example of a quadruple bond is also found in Di-tungsten tetra(hpp).
5. Quintuple bonds have been found to exist in certain dichromium compounds.
6. Sextuple bonds are found in diatomic molybdenum and tungsten.

Most bonding of course, is not localized, so the following classification, while powerful and pervasive, is of limited validity. Three center bonds do not conform readily to the above conventions. Electron atomic and molecular orbitals, showing among others the sigma bond of two s-orbitals and a sigma bond of two p-orbitals In chemistry, sigma bonds (σ bonds) are a type of covalent chemical bond. ... Ethylene (or IUPAC name ethene) is the chemical compound with the formula C2H4. ... Electron atomic and molecular orbitals, showing among others the sigma bond of two s-orbitals and a sigma bond of two p-orbitals In chemistry, sigma bonds (σ bonds) are a type of covalent chemical bond. ... Electron atomic and molecular orbitals, showing a Pi-bond at the bottom right of the picture. ... R-phrases , , , , . S-phrases , , , , , , , , . Flash point −17. ... Covalently bonded hydrogen and carbon in a molecule of methane. ... General Name, Symbol, Number molybdenum, Mo, 42 Chemical series transition metals Group, Period, Block 6, 5, d Appearance gray metallic Standard atomic weight 95. ... General Name, Symbol, Number rhenium, Re, 75 Chemical series transition metals Group, Period, Block 7, 6, d Appearance grayish white Standard atomic weight 186. ... the hpp ligand anion Di-tungsten tetra(hpp) or W2(hpp)4 is a di-tungsten paddlewheel compound with four hpp or hexahydropyrimidopyrimidine ligands. ... A quintuple bond in chemistry is an unusual type of chemical bond first observed in 2005 in a chromium dimer in an organometallic compound. ... REDIRECT [[ Insert text]]EWWWWWWWWWWWWW YO General Name, symbol, number chromium, Cr, 24 Chemical series transition metals Group, period, block 6, 4, d Appearance silvery metallic Standard atomic weight 51. ... A sextuple bond is a type of covalent bond involving 12 bonding electrons. ... General Name, Symbol, Number molybdenum, Mo, 42 Chemical series transition metals Group, Period, Block 6, 5, d Appearance gray metallic Standard atomic weight 95. ... For other uses, see Tungsten (disambiguation). ... In chemistry, a three-center bond is a type of covalent bond, in which one pair of electrons joins three atoms rather than the usual two. ...

Resonance

Many bonding situations can be described with more than one valid Lewis Dot Structure (for example, ozone, O₃). 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. 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. For other uses, see Ozone (disambiguation). ... Resonance structures are diagrammatic tools in organic chemistry to symbolize resonant bonds between atoms in molecules. ...

A special resonance case is exhibited in aromatic rings of atoms (for example, benzene). 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. In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... For benzine, see petroleum ether. ...

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.

Current theory

Today the valence bond model has been supplanted by the molecular orbital model. 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. In chemistry, a molecular orbital is a region in which an electron may be found in a molecule. ...

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.

See also

• Metallic bonding
• Linear combination of atomic orbitals
• Hybridisation
• Hydrogen bond
• Noncovalent bonding
• Disulfide bond

Metallic bonding is intramolecular bonding within metals. ... The linear combination of atomic orbitals molecular orbital method (usually called the LCAO MO method) is a technique for calculating molecular orbitals in quantum chemistry. ... four sp³ orbitals three sp² orbitals In chemistry, hybridisation or hybridization (see also spelling differences) is the concept of mixing atomic orbitals to form new hybrid orbitals suitable for the qualitative description of atomic bonding properties. ... An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ... This article needs to be wikified. ... In chemistry, a disulfide bond is a single covalent bond derived from the coupling of thiol groups. ...

References

1. ^ March, J. “Advanced Organic Chemistry” 4th Ed. J. Wiley and Sons, 1992: New York. ISBN 0-471-60180-2.
2. ^ G. L. Miessler and D. A. Tarr “Inorganic Chemistry” 3rd Ed, Pearson/Prentice Hall publisher, ISBN 0-13-035471-6.
3. ^ Merriam-Webster - Collegiate Dictionary (2000).
4. ^ Langmuir, I. (1919). J. Am. Chem. Soc.; 1919; 41; 868-934.
5. ^ W. Heitler and F. London, Zeitschrift für Physik, vol. 44, p. 455 (1927). English translation in H. Hettema, Quantum Chemistry, Classic Scientific Papers, World Scientific, Singapore (2000).

• Covalent bonding - Single bonds. chemguide (2000).
• Electron Sharing and Covalent Bonds. Department of Chemistry University of Oxford.
• Chemical Bonds. Department of Physics and Astronomy, Georgia State University.

Merriam-Webster, originally known as the G. & C. Merriam Company of Springfield, Massachusetts, is a United States company that publishes reference books, especially dictionaries that are descendants of Noah Websters An American Dictionary of the English Language (1828). ...

External links

• Covalent Bonds and Molecular Structure