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

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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what is the volume occupied by 40 grams of argon gas (ar) at standard conditions? what volume, in liters, is occupied by 1.5 x 1023 

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation: