Question

The coordination number of atoms in a body-centered cubic (BCC) unit cell is:

• A. 4
• B. 6
• C. 8
• D. 12

Hint:

In BCC, think of the body-center atom being connected to all 8 corner atoms — that’s why the coordination number is 8.

Answer 1

The Correct Option is C

The coordination number is the number of nearest neighbor atoms that surround a given atom in a crystal structure. In a BCC (Body-Centered Cubic) Structure:

• Each unit cell consists of 1 atom at the center and 8 corner atoms shared among adjacent unit cells.
• The atom at the center touches all 8 corner atoms.
• Hence, each atom in a BCC structure has 8 nearest neighbors.
• Example materials with BCC structure: Iron (at room temperature), Chromium, Tungsten.

Why the Other Options Are Incorrect:

• (A) 4: This is the coordination number for tetrahedral coordination, not BCC.
• (B) 6: Coordination number of a simple cubic structure.
• (D) 12: Coordination number for a face-centered cubic (FCC) structure.

Therefore, the correct coordination number for a BCC unit cell is 8.