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Key People:Irving LangmuirGilbert N. Lewis...(Show more)Related Topics:conjugated systempi bondsigma bondcatenationoctet rule...(Show more)
covalent bond, in chemistry, the interatomic affiliation that results from the sharing of one electron pair in between two atoms. The binding occurs from the electrostatic attraction of their nuclei because that the very same electrons. A covalent bond creates when the external inspection atoms have actually a lower complete energy 보다 that of extensively separated atoms.
A brief treatment of covalent binding follows. For complete treatment, see chemical bonding: Covalent bonds.
Molecules that have actually covalent linkages encompass the not natural substances hydrogen, nitrogen, chlorine, water, and ammonia (H2, N2, Cl2, H2O, NH3) in addition to all organic compounds. In structural representations of molecules, covalent bond are suggested by solid currently connecting bag of atoms; e.g.,
A single line suggests a bond between two atom (i.e., including one electron pair), double lines (=) suggest a double bond in between two atom (i.e., including two electron pairs), and triple present (≡) stand for a triple bond, together found, for example, in carbon monoxide (C≡O). Single bonds consist of one sigma (σ) bond, double bonds have actually one σ and also one pi (π) bond, and triple bonds have one σ and two π bonds.
Covalent bonds space directional, meaning that atom so external inspection prefer particular orientations family member to one another; this in turn provides molecules definite shapes, together in the angular (bent) framework of the H2O molecule. Covalent bonds in between identical atoms (as in H2) room nonpolar—i.e., electrically uniform—while those in between unlike atoms space polar—i.e., one atom is contempt negatively charged and the various other is contempt positively charged. This partial ionic character of covalent bonds boosts with the difference in the electronegativities of the 2 atoms. See also ionic bond.
When none of the facets in a compound is a metal, no atom in the compound have an ionization power low sufficient for electron loss to be likely. In such a case, covalence prevails. Together a basic rule, covalent binding are formed between aspects lying toward the best in the regular table (i.e., the nonmetals). Molecule of similar atoms, such together H2 and also buckminsterfullerene (C60), are additionally held with each other by covalent bonds.
Lewis formulation of a covalent bond
The idea that 2 electrons deserve to be shared between two atoms and serve as the link between them was very first introduced in 1916 by the American chemist G.N. Lewis, who defined the formation of together bonds as resulting from the tendencies of specific atoms to combine with one another in order because that both to have actually the digital structure of a matching noble-gas atom.
In Lewis state a covalent link is a common electron pair. The bond in between a hydrogen atom and a chlorine atom in hydrogen chloride is formulated together follows:
In a Lewis framework of a covalent compound, the mutual electron pair in between the hydrogen and also chlorine ions is stood for by a line. The electron pair is referred to as a bonding pair; the three other pairs of electrons on the chlorine atom are referred to as lone pairs and also play no direct role in stop the 2 atoms together.
Each atom in the hydrogen chloride molecule attains a closed-shell octet of electron by sharing and hence achieves a maximum lowering the energy. In general, one incomplete shell way that some attracting power of a nucleus may be wasted, and including electrons past a closed shell would entail the energetic disadvantage of start the next shell that the atom concerned. Lewis’s octet rule is again applicable and is checked out to represent the extreme method of achieve lower energy rather 보다 being a goal in itself.
A covalent bond develops if the external inspection atoms have a lower total energy than the extensively separated atoms. The easiest interpretation of the to decrease in energy that occurs when electrons are mutual is that both electron lie in between two attracting centres (the nuclei the the 2 atoms attached by the bond) and also hence lie reduced in energy than once they endure the attraction of a single centre.
See more: Incompatible Types: Possible Lossy Conversion From Double To Int
Lewis frameworks of more complicated molecules have the right to be created quite simply by prolonging the process that has actually been described for hydrogen chloride. First, the valence electrons that are obtainable for bonding room counted (2 × 1 + 6 = 8 in H2O, because that example, and also 4 + 4 × 7 = 32 in carbon tetrachloride, CCl4), and the chemical icons for the elements are put in the setup that shows which room neighbours:
Next, one bonding pair is included between each connected pair the atoms:
The remaining electrons are then added to the atom in such a method that every atom has a share in one octet of electrons (this is the octet-rule part of the procedure):
Finally, each bonding pair is stood for by a dash:
(Note that Lewis structures carry out not necessarily display the actual shape of the molecule, only the topological pattern of their bonds.)
In some older formulations of Lewis structures, a difference was made in between bonds developed by electrons that have actually been gave by both atom (as in H―Cl, where one mutual electron can be regarded as offered by the hydrogen atom and the other by the chlorine atom) and also covalent bonds developed when both electrons deserve to be related to as offered by one atom, together in the development of OH− indigenous O2− and H+. Such a bond was dubbed a coordinate covalent bond or a dative bond and also symbolized O → H−. However, the challenges encountered in the attempt to save track the the beginning of bonding electrons and the ide that a name: coordinates covalent link differs in which method from a covalent link (it does not) have led come this consumption falling right into disfavour.