Explanation:
Type I
These are compounds in which the cation (metal ion) has a fixed charge.
Examples are;
MgO. NaCl
Type II
These are ionic compounds in which the cation (metal ion) has a variable charge.
Examples are;
FeCl3, PbS2
Type III
These are covalent molecules with no cation.
Examples are;
SO3, N2O5
