In electromagnetism, charge density is a measure of electric charge per unit volume of space, in one, two or three dimensions. More specifically: the linear, surface, or volume charge density is the amount of electric charge per unit length, surface area, or volume, respectively. The respective SI units are C·m−1, C·m−2 or C·m−3.
Like any density, charge density can depend on position, but because charge can be negative - so can the density. It should not be confused with the charge carrier density, the number of charge carriers (e.g. electrons, ions) in a material per unit volume, not including the actual charge on the carriers.
In chemistry, it can refer to the charge distribution over the volume of a particle; such as a molecule, atom or ion. Therefore, a lithium cation will carry a higher charge density than a sodium cation due to the lithium cation's having a smaller ionic radius, even though sodium has more electrons (11) than lithium (3).
Read more about Charge Density: Free, Bound and Total Charge, Homogeneous Charge Density, Discrete Charges, Relative Charge Density, Charge Density (quantum Mechanics), Application
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