QRC Chemist Evaluation Practice Exam 2025 - Free Chemist Evaluation Practice Questions and Study Guide

A crystalline solid is characterized by a highly ordered atomic structure, where the atoms are arranged in a repeating, three-dimensional pattern. This regular arrangement leads to distinct physical properties such as sharp melting points, specific symmetrical shapes, and well-defined geometric structures.

The arrangement of atoms in a crystalline solid is not random; instead, it is systematic, resulting in the formation of well-defined crystal lattices. This order at the atomic level is what differentiates crystalline solids from amorphous solids, which lack such long-range order and instead have a more random atomic arrangement.

Additionally, the definition does not restrict crystalline solids to formation at high temperatures; they can form under various conditions depending on the material involved and their cooling process. Thus, the essence of a crystalline solid lies in its ordered atomic structure, making this definition the most accurate among the options.