An alternative representation to 0x45
's rendition of Coulomb's law accounts for the polarizability of the environment:
f = ----------
4 pi E r2
is actually epsilon. E
is known as the dielectric constant
, or relative permittivity
is the permittivity of free space
(of a vacuum).
The dielectric constant, subsumed in the constant k
in the previous writeup, accounts for screening of electrostatic interactions between charges by the environment. An environment that is highly polarizable will orient around a given charge, thereby effectively neutralizing the effects of electric field at long distances. Water has a high dielectric constant - around 80. As a result, ions in water have a much weaker attraction or repulsion than they do in the gas phase.