Which solid type is NaCl (table salt) an example of?

• A. Molecular Solids
• B. Ionic Solids
• C. Covalent-network Solids
• D. Metallic Solids

Answer: (B)

This question tests how solids are classified by the type of bonding that holds their structure together. NaCl is an ionic solid because it forms from a metal and a nonmetal, with sodium transferring an electron to chlorine to create Na+ and Cl− ions. These oppositely charged ions arrange in a repeating lattice and are held together by strong electrostatic (ionic) bonds. That ionic lattice gives NaCl its high melting point and brittle behavior, and explains why it conducts electricity only when molten or dissolved, not as a solid.

This isn’t a molecular solid, since there aren’t discrete molecules bound by intermolecular forces; there’s a continuous lattice of ions instead. It isn’t a covalent-network solid, which would involve a vast network of covalent bonds throughout the structure (as in diamond or SiO2). It also isn’t a metallic solid, which relies on a lattice of positive ions in a sea of delocalized electrons to conduct electricity.