Crystal Structures

Step 1: Simple cubic unit cell.
In a simple cubic unit cell, there is 1 atom at each corner. Since each corner atom is shared by 8 unit cells, the total number of atoms per unit cell is:

Step 2: Face-centered cubic (FCC) unit cell.
In a face-centered cubic unit cell, there are atoms at the 8 corners (each shared by 8 unit cells) and 6 atoms at the centers of the faces (each shared by 2 unit cells). Therefore, the total number of atoms per unit cell is:

Step 3: Body-centered cubic (BCC) unit cell.
In a body-centered cubic unit cell, there is an atom at each corner (shared by 8 unit cells) and 1 atom at the center (not shared). The total number of atoms per unit cell is:

Step 4: Conclusion.
Thus, the number of atoms per unit cell for simple cubic, face-centered cubic, and body-centered cubic unit cells are 1, 4, and 2, respectively. The correct answer is option (1).