Which of the following is a property of covalent compounds?

• A. They conduct electricity in molten state.
• B. They are usually soluble in water.
• C. They form crystalline solids with high lattice energy.
• D. They generally have low melting and boiling points.

Answer: (D)

Verified step by step guidance

1. Understand that covalent compounds are formed by the sharing of electrons between nonmetal atoms, resulting in molecules rather than ions.
2. Recall that covalent compounds typically do not conduct electricity because they lack free ions or electrons to carry charge, even in molten or dissolved states.
3. Recognize that covalent compounds often have low melting and boiling points because the intermolecular forces (like Van der Waals forces or hydrogen bonds) holding the molecules together are weaker than the ionic bonds in ionic compounds.
4. Note that covalent compounds are usually not very soluble in water unless they can form hydrogen bonds or interact strongly with water molecules; many are soluble in nonpolar solvents instead.
5. Understand that crystalline solids with high lattice energy are characteristic of ionic compounds, not covalent compounds, because lattice energy arises from strong electrostatic attractions between ions.