The different models used to represent substances have different features and limitations. For example, the model of the metallic lattice usually shown does not show more than one layer of metal ions, or that the delocalised electrons are in constant motion.
Ionic compounds form a regular lattice structure in which oppositely charged ions are strongly attracted to each other. Sodium chloride is an ionic compound. The table shows some limitations of models.
The atoms in a simple molecular substance are joined together by strong covalent bonds. Molecules are attracted to each other by weak intermolecular forces. Water is a simple molecular substance. The table shows some limitations of different models of water.