Which of the following is NOT a property of an ionic compound?

• A. They have high melting and boiling points.
• B. They conduct electricity when dissolved in water.
• C. They are malleable and ductile.
• D. They form crystalline solids at room temperature.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the nature of ionic compounds. Ionic compounds are formed by the electrostatic attraction between positively charged cations and negatively charged anions.
2. Step 2: Recall the typical properties of ionic compounds: they usually have high melting and boiling points due to strong ionic bonds, they conduct electricity when molten or dissolved in water because ions are free to move, and they form crystalline solids at room temperature because of the regular arrangement of ions.
3. Step 3: Consider the property of malleability and ductility. These properties are characteristic of metallic bonds, where atoms can slide past each other without breaking the bond, allowing metals to be shaped without breaking.
4. Step 4: Compare this with ionic compounds, which are brittle rather than malleable or ductile because when ions are displaced, like charges repel and the crystal lattice breaks.
5. Step 5: Conclude that the property 'They are malleable and ductile' is NOT a property of ionic compounds, distinguishing them from metals.