Which type of solid can become an electrical conductor via chemical substitution?

Covalent-network solids

The right answer is ionic solids

An ionic solid is a solid composed of ions. The ionic solid also called ionic crystal is an ordered assembly of anion and cation (negative and positive charge respectively). Since such a solid is always electrically neutral, it always associates cations and anions whose charges compensate each other.

Covalent-bond does not have negative and positive charges, so it cannot conduct electricity.

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