Question

Which among the following mentioned in the options do not conduct electricity?
A. Cu (metal)
B. NaCl (aq)
C. NaCl (molten)
D. NaCl (solid)

Answer 1

Hint: For a material to conduct electricity, charged particles such as free electrons or ions should have free movement across a material or substance. The presence of free electrons in materials such as metals make them excellent conductors of electricity. The aqueous and molten states of materials contain ions, the presence of which aids in the conduction of electricity.

Complete step-by-step solution:
Good conductors are those that conduct electricity. Poor conductors or insulators are those that cannot conduct electricity.
The presence of free electrons or ions in a material assists in the conduction of electricity
Because of the presence of free electrons in materials such as metals such as copper, they are good conductors of electricity. The presence of delocalized electrons in metals are useful for the conduction of electricity and heat.
The aqueous state of NaCl contains ions that assist in the conduction of electricity. Dissociation of salts into ions takes place when these ions are dissolved into water. Thereby allowing charges to flow and conduct electricity.
The molten state of NaCl contains free ions (not as much as in the aqueous state) which allow electricity to be conducted through the material.
NaCl in the solid-state have tightly bound electrons which restrict the flow of electrons. Also in the solid-state NaCl does not dissociate into ions. Hence, it is not a conductor of electricity.
Option (D) NaCl in the solid-state.

Note: NaCl in solid-state is otherwise mentioned as common salt. In addition to the conduction of electricity, conductors also transmit heat. Metals such as copper, aluminium, gold and aqueous solutions are good conductors of electricity. The presence of valence electrons determines whether a material is a good conductor of electricity or a poor conductor. The materials that have eight valence electrons are poor conductors.