Determine about the silicate clays
The silicate clays develop charges because of an imbalance which takes place due to an exchange of one cation by the other in the crystal structure. The charge which develops may be positive or negative. For example, a positive charge would develop when Al3+ replaces a Mg2+ ion and a negative charge would be developed when it is the other way round. There are some pH dependent charges also which develop due to either an excess or low concentration of OH- and H+ ions. Due to the presence of cations in silicate clays, they are capable of exchanging their ions with the ones in soil solution. The exchange is easy in case the particle size of exchanger is very small and this is true with clays.