Polarization of an Atom

Claimed by Owen Fisher

This page serves to outline and explain the inner workings and hidden mechanisms of the polarization of an atom.

The Main Idea

In an atom, the cloud of electrons, while connected to the nucleus, is not exactly centered on the nucleus. For this reason, atoms can interact with external charges and become polarized. The nucleus and cloud of electrons can move relative to each other. If an external charge comes into the same space that an atom occupies or is close by, the charge creates an electric field, which exerts a force on the atom. "Applied" electric fields such as this explain why the electron cloud and nucleus can move relative to each other. For example, if a positive charge is placed to the left of an atom, an electric field will be created that shifts the electron cloud of the atom towards the positive charge (to the left) and will shift the net positive nucleus away from the charge (to the right) as two objects of the same charge repel each other. In this case, it is now more probable to find an electron to the left of the nucleus, rather than the right.

A Mathematical Model

[math]\displaystyle{ {\vec{F} = q\vec{E}} }[/math] where F is the force created by the electric field E and the charge of a particle q. This force is what causes the atom to become polarized.

[math]\displaystyle{ {\vec{p} = α\vec{E}} }[/math] for almost all materials, the dipole moment p of the polarized atoms or molecules is directly proportional to the magnitude of the applied electric field E. The constant α is called the "polarizability" of a particular material. Many of these polarizability values have been measured experimentally and can be found in reference volumes.