Based on the Solid Pack Categories of Solids Based on Bonds that Hold the Solid Together Categories of Solids Based on the Solid Pack Solids can be divided into three categories on the basis of how the particles that form the solid pack.
Crystalline solids are three-dimensional analogs of a brick wall.
They have a regular structure, in which the particles pack in a repeating pattern from one edge of the solid to the other. Polycrystalline solids are an aggregate of a large number of small crystals or grains in which the structure is regular, but the crystals or grains are arranged in a random fashion. The extent to which a solid is crystalline has important effects on its physical properties. Milk bottles are made from a more crystalline form of polyethylene, and they have a much more rigid structure. Together Solids can be classified on the basis of the bonds that hold the atoms or molecules together.