Abstract: Classification of crystalline solids is one of the basic contents in general chemistry courses. This article elucidates the various interactions between anions and cations in different ionic crystals, showing that these interactions may include not only ionic bonds but also hydrogen bonds and Van der Waals force. Therefore, the statement that ionic crystals are solely formed through ionic bonds between anions and cations is inaccurate. It is necessary to re-examine the definition of ionic crystals in general chemistry, and to consider how different types of ionic interactions affect the properties of ionic crystals, such as their melting and boiling points.

Key words: Distance between atoms, Interaction between ions, Ionic bond, Hydrogen bond, Van der Waals force