The correct option is Molten state or in aqueous solution.
Explanation
Ionic compounds consist of a lattice of positively charged cations and negatively charged anions held together by strong electrostatic forces. For any substance to conduct electricity, it must contain charged particles (ions or electrons) that are free to move and carry charge.
Analysis of States
- Solid State: In the solid phase, ions are locked into fixed positions within a rigid crystal lattice due to strong electrostatic attraction. Because the ions are immobile, they cannot conduct electricity. Therefore, options suggesting the solid state or dry powdered state are incorrect.
- Molten (Liquid) State: When an ionic compound is melted, heat energy overcomes the electrostatic forces holding the lattice together. This breaks the crystal structure, allowing the ions to move freely and conduct electricity.
- Aqueous Solution: When dissolved in water, the polar water molecules interact with the ions, reducing the attractive forces between them. This causes the ions to dissociate and become hydrated. These free-moving hydrated ions allow the solution to conduct electricity effectively.
Key Takeaway: Ionic compounds act as insulators in the solid state due to the absence of free ions but become good conductors in the molten state or aqueous solution when ions become mobile.