Final answer:
A crystalline material is a solid with a regular, repeating arrangement called a crystal lattice. It exhibits uniform properties, including a distinct melting point, in contrast to amorphous solids.
Step-by-step explanation:
When we say that a material is "crystalline", we are referring to a solid substance in which the atoms, molecules, or ions are packed in a regular, ordered arrangement that extends in all three spatial dimensions. This arrangement is known as a crystal lattice. Most naturally occurring and synthetic solids are crystalline because a regular particle arrangement allows for maximized attractive interactions between particles, which also leads to a minimization of total intermolecular energy.
This efficient packing results in solids that exhibit uniform properties throughout the material. The various types of crystalline solids—which include ionic, metallic, covalent network, and molecular solids—differ in terms of the particles they contain, how these particles are arranged, and the strength of the attractive forces between them. This leads to distinct physical characteristics such as sharp melting points for crystalline solids, as opposed to amorphous solids, which do not have a regular internal structure and melt over a range of temperatures. Additionally, the presence of defects within the crystalline structure, like vacancies or impurities, can influence properties such as electrical conductivity, which is an important consideration in semiconductor manufacturing.