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Polarizability
 
 
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Polarizability is the relative tendency of a charge distribution, like the electron cloud
Electron cloud

Electron cloud is not a term used by the Nobel Prize laureate and acclaimed educator Richard Feynman in The Feynman Lectures on Physics for discussing "exactly what is an electron?"....
 of an atom
Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
 or molecule
Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
, to be distorted from its normal shape by an external electric field
Electric field

In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field ....
, which may be caused by the presence of a nearby ion
Ion

An ion is an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. According to the Bohr_model this will be from or in the outer shield 'n'....
 or dipole
Dipole

In physics, there are two kinds of dipoles :*An electric dipole is a separation of positive and negative charge. The simplest example of this is a pair of electric charges of equal magnitude but opposite sign, separated by some, usually small, distance....
.

The electronic polarizability 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 polarizability volume with units of cm3 or in Å3 = 10-24 cm3.

where is the vacuum permittivity
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 polarization in response to the field, and thereby reduce the total electric field inside the material....
.

The polarizability of individual particles is related to the average electric susceptibility
Electric susceptibility

The electric susceptibility ?e of a dielectric material is a measure of how easily it polarization density in response to an electric field....
 of the medium by the Clausius-Mossotti relation
Clausius-Mossotti relation

The Clausius?Mossotti equation is named after the Italian physicist Ottaviano-Fabrizio Mossotti, whose 1850 book analyzed the relationship between the dielectric constants of two different media, and the German physicist Rudolf Clausius, who gave the formula explicitly in his 1879 book in the context not of dielectric constants but of indices...
.

Note that the polarizability as defined above is a scalar
Scalar (physics)

In physics, a scalar is a simple physical quantity that is not changed by coordinate system rotations or translations , or by Lorentz transformations or space-time translations ....
 quantity.






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Polarizability is the relative tendency of a charge distribution, like the electron cloud
Electron cloud

Electron cloud is not a term used by the Nobel Prize laureate and acclaimed educator Richard Feynman in The Feynman Lectures on Physics for discussing "exactly what is an electron?"....
 of an atom
Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
 or molecule
Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
, to be distorted from its normal shape by an external electric field
Electric field

In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field ....
, which may be caused by the presence of a nearby ion
Ion

An ion is an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. According to the Bohr_model this will be from or in the outer shield 'n'....
 or dipole
Dipole

In physics, there are two kinds of dipoles :*An electric dipole is a separation of positive and negative charge. The simplest example of this is a pair of electric charges of equal magnitude but opposite sign, separated by some, usually small, distance....
.

The electronic polarizability 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 polarizability volume with units of cm3 or in Å3 = 10-24 cm3.

where is the vacuum permittivity
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 polarization in response to the field, and thereby reduce the total electric field inside the material....
.

The polarizability of individual particles is related to the average electric susceptibility
Electric susceptibility

The electric susceptibility ?e of a dielectric material is a measure of how easily it polarization density in response to an electric field....
 of the medium by the Clausius-Mossotti relation
Clausius-Mossotti relation

The Clausius?Mossotti equation is named after the Italian physicist Ottaviano-Fabrizio Mossotti, whose 1850 book analyzed the relationship between the dielectric constants of two different media, and the German physicist Rudolf Clausius, who gave the formula explicitly in his 1879 book in the context not of dielectric constants but of indices...
.

Note that the polarizability as defined above is a scalar
Scalar (physics)

In physics, a scalar is a simple physical quantity that is not changed by coordinate system rotations or translations , or by Lorentz transformations or space-time translations ....
 quantity. This implies that the applied electric fields can only produce polarization components parallel to the field. For example, an electric field in the -direction can only produce an component in . However, it can happen that an electric field in the -direction, produces a or component in the vector . In this case is described as a tensor
Tensor

A tensor is an object which extends the notion of Scalar , Vector , and Matrix . The term has slightly different meanings in mathematics and physics....
 of rank 2, which is represented with respect to a given system of axes (frame of reference) by a 33 matrix
Matrix (mathematics)

In mathematics, a matrix is a rectangular array of numbers, as shown at the right. In addition to a number of elementary, entrywise operations such as matrix addition a key notion is matrix multiplication....
.

See also

  • Polarization density
    Polarization density

    In classical electromagnetism, the polarization density is the vector field that expresses the density of permanent or induced electric dipole moments in a dielectric material....