What term describes solid forms that contain ordered units?

The term that describes solid forms containing ordered units is crystalline solids. This type of solid has a well-defined geometric arrangement, where the atoms, ions, or molecules are arranged in a highly ordered structure, extending in a three-dimensional space. This order leads to distinctive properties, such as a specific melting point and optical characteristics, which distinguish crystalline solids from their disordered counterparts.

In crystalline solids, the regular pattern in which particles are arranged allows for the formation of a lattice structure, giving rise to repeating units that contribute to the material's stability and its reliable physical properties. This is crucial in the pharmaceutical sciences, as the crystalline form can significantly affect a drug's solubility, stability, and overall bioavailability.

Understanding the ordered nature of crystalline solids is foundational for topics that involve solid-state chemistry and material sciences, particularly in developing effective pharmaceutical formulations.