What distinguishes a crystalline solid from a non-crystalline solid?

A crystalline solid is characterized by its defined geometric structure, which stems from the orderly and repeating arrangement of its particles. This regular pattern extends in three dimensions and typically results in a solid with flat surfaces and sharp edges. This ordered arrangement allows for unique physical properties, such as distinct melting points and well-defined angles between crystal faces, which can be observed in substances like salt or quartz.

In contrast, non-crystalline solids, or amorphous solids, lack this long-range order and have a more random arrangement of particles, leading to more varied properties. While there are many types of particles that can make up crystalline solids, the distinct geometric arrangement of those particles to form a lattice structure is what sets them apart fundamentally from their non-crystalline counterparts.

The other choices incorrectly describe aspects of crystalline and non-crystalline solids. For instance, the idea that non-crystalline solids do not contain any particles is misleading, as they indeed consist of atoms or molecules, just arranged differently than in crystalline solids. Thus, the correct understanding centers on the defined geometric structure that characterizes crystalline solids.