In a Simple Cubic lattice, what fraction of each corner atom contributes to the unit cell?

• A. 1/8
• B. 1/4
• C. 1/2
• D. 1

Answer: (A)

In a simple cubic lattice, atoms sit at the eight corners of the unit cell, and each corner atom is shared among eight neighboring unit cells. So only 1/8 of a corner atom belongs to any given unit cell. With eight corners, the total contribution is 8 × 1/8 = 1 atom per unit cell, which also explains why a simple cubic cell has one atom effectively inside it. The 1/4 or 1/2 or 1 options would correspond to sharing with fewer or more cells than the actual eight-way sharing at a corner, which doesn’t apply to this structure.