A body-centered cubic unit cell contains how many atoms total?

A body-centered cubic unit cell contains how many atoms total?

• A. 1
• B. 2
• C. 3
• D. 4

Answer: (B)

In a body-centered cubic structure, count atoms by adding the atom in the center to the portions of the eight corner atoms that lie at the cube’s corners. Each corner atom is shared by eight neighboring unit cells, so it contributes 1/8 to this unit cell. Eight corners contribute 8 × 1/8 = 1 atom. The center atom is entirely inside the unit cell, contributing 1 more. Total atoms per unit cell = 1 + 1 = 2. This differs from a simple cubic cell (1 atom per cell) and a face-centered cubic cell (4 atoms per cell).

In a body-centered cubic structure, count atoms by adding the atom in the center to the portions of the eight corner atoms that lie at the cube’s corners. Each corner atom is shared by eight neighboring unit cells, so it contributes 1/8 to this unit cell. Eight corners contribute 8 × 1/8 = 1 atom. The center atom is entirely inside the unit cell, contributing 1 more. Total atoms per unit cell = 1 + 1 = 2. This differs from a simple cubic cell (1 atom per cell) and a face-centered cubic cell (4 atoms per cell).