Which of the following describes an ionic compound?

An ionic compound is best described as having a repeating unit of charged ions. This characteristic arises from the way ionic compounds are formed, which involves the transfer of electrons from one atom to another. Typically, this results in the formation of cations (positively charged ions) and anions (negatively charged ions) that are held together by strong electrostatic forces of attraction. The arrangement of these ions creates a crystalline lattice structure, where the repeating units reflect the regular pattern of alternating positive and negative charges throughout the compound.

The other options describe different types of compounds or behaviors that do not accurately portray the nature of ionic compounds. For instance, while covalent bonds do involve molecules, ionic compounds do not consist of discrete molecules; rather, they exist as an extended lattice of ions. Ionic compounds are generally solids at room temperature, with many being soluble in water and not existing as gases. Moreover, although ionic compounds can conduct electricity when dissolved in water or molten (due to the ions being free to move), they do not conduct electricity in their solid state because the ions are confined in the lattice and cannot move freely. Thus, the description of ionic compounds as having a repeating unit of charged ions correctly captures their essential structure and properties.