Surface charge
![Multiple layers of negative charge accumulate near a positively charged surface to form a double layer.](/Images/godic/202502/14/Guoy-Chapman_Double_Layer1632.png")
![A simplified overlay of multiple layers of ions, and electric potential with increasing Debye length. The first layer of absorbed ions is referred to as the inner Helmholtz plane. Next is a layer of non-specifically absorbed, hydrated counterions which represent an outer Helmholtz plane.[1]](/Images/godic/202502/14/Stern_Layer1632.png")
![Diagram depicting electro-osmosis through a glass capillary submerged in an aqueous solution.](/Images/godic/202502/14/Electro-osmosis1632.png")
Surface charge is the electrical potential difference between the inner and outer surface of the dispersed phase in a colloid. There are many different processes which can lead to a surface being charged, including adsorption of ions, protonation/deprotonation, and the application of an external electric field. Surface charge causes a particle to emit an electric field, which causes particle repulsion and attraction, affecting many colloidal properties.