Question

The correct order of co-ordination number in BCC, FCC and HCP unit cells is

• A. 12, 8, 6
• B. 8, 12, 12
• C. 6, 8, 12
• D. 12, 6, 8

Hint:

A higher coordination number indicates more efficient packing. FCC and HCP structures, with a coordination number of 12, have the highest packing efficiency (~74%).

Answer 1

The Correct Option is B

The coordination number refers to the number of nearest neighboring atoms surrounding a given atom in a unit cell. Higher coordination numbers typically indicate more efficient packing, as atoms are packed more closely together. - Body-Centered Cubic (BCC): The coordination number is 8, as each atom is surrounded by 8 nearest neighbors. - Face-Centered Cubic (FCC): The coordination number is 12, as each atom is surrounded by 12 nearest neighbors. - Hexagonal Close-Packed (HCP): The coordination number is also 12, similar to FCC, as atoms are arranged in the most efficient packing configuration. Conclusion: The correct order of coordination numbers is \( 8, 12, 12 \) for BCC, FCC, and HCP, respectively.