Which statement about ionic compounds is true?

Which statement about ionic compounds is true?

• A. They conduct electricity when dissolved in water, but not when molten.
• B. They are always liquids at room temperature.
• C. Ionic compounds form crystalline lattices with high melting points.
• D. They are always solids.

Answer: (C)

Ionic compounds are held together by strong electrostatic forces between oppositely charged ions arranged in a repeating crystal lattice. This lattice creates a rigid solid, since the ions are bound in many directions by these forces. Because so many strong bonds must be overcome to break the lattice, a large amount of energy is required to melt the substance, giving ionic compounds their high melting points. In the solid state the ions can’t move, so they don’t conduct electricity; they only conduct when melted or dissolved in water, where the ions are free to move. So, the true statement is that ionic compounds form crystalline lattices with high melting points.

Ionic compounds are held together by strong electrostatic forces between oppositely charged ions arranged in a repeating crystal lattice. This lattice creates a rigid solid, since the ions are bound in many directions by these forces. Because so many strong bonds must be overcome to break the lattice, a large amount of energy is required to melt the substance, giving ionic compounds their high melting points. In the solid state the ions can’t move, so they don’t conduct electricity; they only conduct when melted or dissolved in water, where the ions are free to move. So, the true statement is that ionic compounds form crystalline lattices with high melting points.