International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

How is an ionic compound, such as sodium chloride, structured?

1. In a linear arrangement of atoms

2. As a giant structure held together by ionic attractions

3. In a molecular cluster of discrete molecules

4. In a layered structure with covalent bonds

The correct answer is: As a giant structure held together by ionic attractions

An ionic compound, such as sodium chloride (NaCl), is structured as a giant lattice formed by a regular arrangement of ions. In this structure, sodium ions (Na⁺) and chloride ions (Cl⁻) alternate and pack together in a three-dimensional framework. The key characteristic of this arrangement is that it is held together by the strong electrostatic forces of attraction between the positively charged sodium ions and the negatively charged chloride ions, known as ionic bonds. This framework creates a stable and rigid structure, which is why ionic compounds typically have high melting and boiling points. The giant lattice structure allows for each ion to be surrounded by multiple oppositely charged ions, resulting in a continuous network that extends throughout the entire crystal. This structure is markedly different from molecular clusters, which consist of discrete molecules that do not have the same extensive bonding network, or layered structures where covalent bonds are prevalent. Overall, the giant ionic lattice in sodium chloride exemplifies how ionic compounds are characterized by their arrangement of ions and the strength of their ionic attractions.