In a face-centered cubic unit cell, how many atoms are present per unit cell?

A unit cell is the smallest repeating unit in a crystal lattice. In a face-centered cubic (FCC) unit cell, atoms are located at each corner and in the center of each face.

• Each of the 8 corner atoms contributes 1/8 to the unit cell (8 * 1/8 = 1 atom).
• Each of the 6 face-centered atoms contributes 1/2 to the unit cell (6 * 1/2 = 3 atoms).
• Correct Option B: 4. The total number of atoms per unit cell in an FCC structure is 1 (from corners) + 3 (from faces) = 4 atoms.
• Option A: 2 is the number of atoms in a body-centered cubic (BCC) unit cell.
• Option C: 6 is incorrect; it represents the number of face-centered atoms, not the total.
• Option D: 8 is the number of corner atoms, but each only contributes a fraction.