Polarizability is the relative tendency of the electron cloud of an atom to be distorted from its normal shape by the presence of a nearby ion or dipole--that is, by an external electric field. Electron cloud is a term used for introducing the concept of wavefunction in low-level pedagogical introductions to atomic physics, molecular physics, chemistry or quantum chemistry. ... Properties In chemistry and physics, an atom (Greek άτομον meaning indivisible) is the smallest possible particle of a chemical element that retains its chemical properties. ... // An ion is an atom or a group of atoms (a chemical substance), or subatomic particle, with a net electric charge. ... The Earths magnetic field, which is approximately a dipole. ... In physics, an electric field or E-field is an effect produced by an electric charge (or a time-varying magnetic field) that exerts a force on charged objects in the field. ...

The electronic polarizability α is defined as the ratio of the induced dipole moment of an atom to the electric field that produces this dipole moment.

Polarizability has the SI units of C⋅m²⋅V^-1 = A²⋅s⁴⋅kg^-1 but is more often expressed as polarizabilty volume with units of cm³ or in ų = 10^-24 cm³.

where ε₀ is the vacuum permittivity. Permittivity is a physical quantity that describes how an electric field affects and is affected by a dielectric medium and is determined by the ability of a material to polarize in response to an applied electric field, and thereby to cancel, partially, the field inside the material. ...

The polarizability of individual particles is related to the average electric susceptibility of the medium by the Clausius-Mossotti relation. It has been suggested that this article or section be merged into permittivity. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

Note that the polarizability α as defined above is a scalar quantity. This implies that the applied electric fields can only produce polarization components parallel to the field. For example, an electric field in the x-direction can only produce an x component in . However, it can happen that an electric field in the x-direction, produces a y or z component in the vector . In this case α is best described as a matrix or a tensor of rank 2. The term scalar is used in mathematics, physics, and computing basically for quantities that are characterized by a single numeric value and/or do not involve the concept of direction. ... Look up matrix in Wiktionary, the free dictionary. ... In mathematics, a tensor is (in an informal sense) a generalized linear quantity or geometrical entity that can be expressed as a multi-dimensional array relative to a choice of basis; however, as an object in and of itself, a tensor is independent of any chosen frame of reference. ...

See also

• Polarization density