Electrovalent compounds, also known as ionic compounds, are formed by the complete transfer of electrons between atoms, resulting in the formation of ions. These ions are held together by strong electrostatic forces of attraction in a crystal lattice structure.

Why (C) is correct:

Ionic compounds conduct electricity in their molten (fused) state or when dissolved in a suitable solvent because their ions become mobile and can carry charge. In the solid state, the ions are fixed in the lattice and cannot move, so they do not conduct electricity.

Option Analysis:

• A) have low melting point: This is incorrect. Due to the strong electrostatic forces between ions, a large amount of energy is required to break the crystal lattice, resulting in high melting points for ionic compounds.
• B) have low boiling point: This is incorrect. Similar to melting points, ionic compounds have very high boiling points because even more energy is needed to overcome the strong interionic forces and separate the ions into the gaseous state.
• D) insoluble in polar solvent: This is incorrect. Ionic compounds are generally soluble in polar solvents like water. The polar water molecules interact with the ions, surrounding them and overcoming the electrostatic forces holding the ions together in the crystal lattice. This process is called solvation.

Correct Answer: (C)