Question

Molten sodium chloride conducts electricity due to presence of:
A. Free electrons
B. Free molecules
C. Atoms
D. Free ions

Answer 1

Hint- In order to conduct electricity a substance must have charge particles, such as electrons and ions that are free to move freely through it. Use this concept to reach the answer.

Complete answer:
Sodium is a metal. Metals atoms have a sea of electrons. These electrons can move and conduct electricity. In addition the atoms in the metal are charged with cations or positivity. The sea of electrons is a perfect visualization of a large molecular orbital where the negative charges match the positive charges of the atoms which allow electrons to float or conduct electricity between atoms.
Sodium ions are represented with one positive sign as $N{a^ + }$ and chloride ions are represented with one negative sign as $C{l^ - }$ which are responsible for carrying current in molten sodium chloride.
Sodium chloride is a salt. In the solid state the sodium valence electron has moved into the chloride atom where it remains in the chlorine atomic orbitals. So the electrons cannot flow. The crystal consists of stiff, electrostatic bonds.
If the solid is melted, however, then the cations $N{a^ + }$ and anions $C{l^ - }$ can move and carry a charge. So a molten salt powers electricity.
Hence, molten sodium chloride conducts electricity due to the presence of free ions.

So, the correct answer is option D.

Note- The flow of electricity in chemical compounds can be due to free electrons as well as free ions. Free ions are the ions, such as found in an ionized gas, whose properties, such as spectrum and magnetic moment, are not significantly affected by other atoms, ions, or molecules nearby. The electrons which are not bound to the nucleus of an atom and which are free to travel by adding external energy are called free electrons. In a material the flow of free electrons is called an electrical current. The electrons traveling free will transfer electric current from one point to another.