Final answer:
The 'S' in base-centered crystals stands for 'side,' referring to the crystal structure where parts are centered at the faces of the unit cell's base or side.
This is distinct from body-centered and face-centered structures found in other crystal systems.
Step-by-step explanation:
The 'S' in a, b, or c base-centered crystals stands for 'side.' This refers to one of the ways that crystals can be structured. In base-centered unit cells of a crystal, parts of the structure are located at the center of two opposite faces.
It's important to differentiate this from other types of unit cell structures, such as body-centered or face-centered cubic units, each with different arrangements of atoms or molecules.
The base-centered crystals are a type of monoclinic crystal system that have atoms at the corners of the cell and in the middle of the bases or sides of the unit cell.
This means the 'b' part of the cell is where the centering occurs. In contrast, the body-centered crystals have an atom in the center of the entire unit cell and face-centered crystals have atoms in the center of each face of the unit cell.