Potassium Chloride solid does not conduct electricity because

Analyze the question: We are asked why solid potassium chloride (KCl) cannot conduct electricity.

Concept: For a substance to conduct electricity, it must contain charge carriers that are free to move. In metals, these are delocalised electrons. In ionic compounds, they are ions, but only when the ions can move, that is, when the compound is molten or dissolved in water.

Step-by-step solution:

1. KCl is formed by the transfer of an electron from potassium to chlorine. It is an ionic compound made of K⁺ and Cl⁻ ions.
2. In the solid state, these ions are held in fixed positions in a crystal lattice by strong electrostatic forces of attraction (the "cohesive forces").
3. Because the ions are locked in position, they cannot move to carry charge, so solid KCl does not conduct.

Checking each option:

• A. It is a covalent compound. Wrong. KCl is ionic, not covalent.
• B. Strong cohesive forces make its ions immobile. Correct. This is exactly the reason the ions cannot move in the solid state.
• C. Strong cohesive force makes its molecule immobile. Wrong. Ionic compounds do not exist as discrete molecules. They form giant ionic lattices.
• D. Each of potassium and chlorine structures contain noble gas structure. This is true of K⁺ and Cl⁻, which both have the argon configuration. But it explains why the ions are stable, not why the solid fails to conduct.

Answer: B

Exam tip: Remember that ionic solids do not conduct, but molten or aqueous ionic compounds do. The key phrase is "ions are not free to move" in the solid state. Whenever you see "ionic solid + no conduction," look for the option about immobile ions.