Which of the following best describes the properties of an ionic compound?

• A. They exist as discrete molecules and are usually gases at room temperature.
• B. They are malleable and ductile, and conduct electricity in the solid state.
• C. They have high melting and boiling points and conduct electricity when dissolved in water.
• D. They have low melting points and are poor conductors of electricity in any state.

Answer: (C)

Verified step by step guidance

1. Recall the general characteristics of ionic compounds: they are composed of positively and negatively charged ions held together by strong electrostatic forces in a lattice structure.
2. Understand that ionic compounds do not exist as discrete molecules; instead, they form extended networks, which contributes to their physical properties.
3. Recognize that ionic compounds typically have high melting and boiling points due to the strong ionic bonds that require significant energy to break.
4. Note that ionic compounds are usually solid at room temperature and are brittle rather than malleable or ductile, which are properties of metallic substances.
5. Remember that ionic compounds conduct electricity when molten or dissolved in water because the ions are free to move and carry charge, but they do not conduct electricity in the solid state where ions are fixed in place.