Question

If a trivalent atom replaces a few silicon atoms in three-dimensional network of silicon dioxide, what would be the type of charge on overall structure?

Answer 1

If a few tetrahedral Si atoms in a three-dimensional network structure of SiO₂ are replaced by an equal number of trivalent atoms, then one valence electron of each Si atom will become free. As a result, each substitution of Si atom by a trivalent atom introduces one unit negative charge into the three-dimensional network structure of SiO₂. Hence, SiO₂ becomes negatively charged.