Chemical bond

A chemical bond is the phenomenon of atoms being held together to form molecules or crystals. All chemical bonds result from electrostatic interactions and/or from sharing of electrons, and derive from the action of the electromagnetic force. Where the electromagnetic force is one of the four fundamental interactions of the physical universe. Electrostatic forces arise from the coulombic attraction or repulson between charged particles. On the other hand the sharing of electrons is described by quantum mechanics in Valence bond theory and Molecular orbital theory.

There are 5 different types of chemical bonds that we use to categorize bonding. Actual bonds may have have properties that aren't so discretely categorized, so a given bond could be defined by more than one of these terms.

The Five Categories

• Ionic bond

Main article: ionic bond In an ionic bond monatomic or polyatomic Ions are held together by electrostatic forces to form a three dimensional crystal lattice structure.

• Covalent bond

Main article: covalent bond Atoms are covalently bonded together by sharing pairs of electrons.

• Coordinate covalent bond

Main article: coordinate covalent bond In this type of covalent bond both shared electrons originate on one of the atoms invovlved in the bond.

• Metallic bond

Main article: metallic bond Here the metal atoms are held together in a three dimensional lattice by the delocalization of the valence electons in energy bands.

• Hydrogen bond

Main article: hydrogen bond This is a type of intermolecular force acting between hydrogen and either nitrogen, oxygen, or Fluorine

The electrons in the MO of a bond are said to be either “localized” on certain atom(s) or “delocalized” between two or more atoms. The type of bond between two atoms is defined by how much the electron density is localized or delocalized among the atoms of the substance.

Many simple compounds involve covalent bonds. These molecules have structures that can be predicted using valence bond theory, and the properties of atoms involved can be understood using concepts such as oxidation number. Other compounds that involve ionic structures can be understood using theories from classical physics. However, more complicated compounds such as metal complexes cannot be described by valence bond theory, and we need quantum chemistry (based on quantum mechanics) to help us understand these molecules.

In the case of ionic bonding, electrons are mainly localized on the individual atoms, and electrons do not travel between the atoms very much. Each atom is assigned an overall electric charge to help us conceptualize the MO's distribution. The forces between atoms (or ions) are largely characterized by isotropic continuum electrostatic potentials.

By contrast, in covalent bonding, the electron density within bonds is not assigned to individual atoms, but is instead delocalized in the MOs between atoms. The widely-accepted theory of the linear combination of atomic orbitals (LCAO) helps describe the MOs' structures and energies based on the AOs of the atoms they came from. Unlike pure ionic bonds, covalent bonds may have directed anisotropic properties.

Atoms can also form bonds that are intermediates between ionic and covalent. This is because these definitions are based on the extent of electron delocalization. Electrons can be partially delocalized between atoms, but spend more time around one atom than another. This type of bond is often called “polar covalent”.

These chemical bonds are intramolecular forces that keep atoms held together in molecules. There are also intermolecular forces that cause molecules to be attracted or repulsed by each other. These forces include ionic interactions, hydrogen bonds, dipole-dipole interactions, and induced dipole interactions.

Linus Pauling's book The Nature of the Chemical Bond is perhaps the most influential book on chemistry ever published.

References

ISBN links support NWE through referral fees

• W. Locke (1997). Introduction to Molecular Orbital Theory. Retrieved May 18, 2005.
• Carl R. Nave (2005). HyperPhysics. Retrieved May 18, 2005.

---

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

• Chemical bond  ^history

The history of this article since it was imported to New World Encyclopedia:

• History of "Chemical bond"

Note: Some restrictions may apply to use of individual images which are separately licensed.