What type of solid is characterized by a lack of long-range order?

The correct type of solid characterized by a lack of long-range order is an amorphous solid. Amorphous solids do not possess a well-defined geometric structure or long-range periodicity in their arrangement of atoms or molecules. Unlike crystalline solids, which have an ordered and repeating arrangement of particles, amorphous solids exhibit a random and disordered arrangement.

This inability to form a long-range structure means that amorphous solids do not show distinct melting points; instead, they soften over a range of temperatures. Common examples of amorphous solids include glass and certain types of plastics.

The other types of solids mentioned, such as crystalline solids, have a regular arrangement and long-range order, while polycrystalline solids contain multiple small crystals or grains, each showing some degree of organization. Metalloid solids refer to elements that have properties intermediate between metals and nonmetals, which doesn’t pertain directly to the structural characteristics of solids in terms of order.