the anion, which then requires extra cations. For example, in the mineral orthoclase , the anion is a tridimensional network of tetrahedra in which all oxygen corners are shared. If all tetrahedra had silicon centers, the anion would be just neutral silica . Replacement of one in every four silicon atoms by an aluminum atom results in the anion , whose charge is neutralized by the potassium cations .

Main groups