Which term groups crystals by symmetry and internal structure?

• A. Crystalline
• B. Crystal Systems
• C. Crystal Planes
• D. Glide Plane

Answer: (B)

Crystals are grouped by how their internal lattice is arranged and the symmetry that arrangement exhibits. The term that does this grouping is Crystal Systems. It classifies crystals into seven systems—cubic, tetragonal, orthorhombic, hexagonal, trigonal, monoclinic, and triclinic—based on the geometry of the unit cell and the presence of symmetry elements. This reflects both the symmetry and the internal structure of the crystal.

Crystalline describes the material’s ordered, repeating structure in general, not a specific way of classifying by symmetry. Crystal Planes refer to the faces of a crystal and are described by Miller indices, not a broad classification. Glide Plane is a specific symmetry operation in a lattice, not a category of crystals.