Question

What is the coordination number in a Hexagonal Close-Packed (hcp) structure?

• A. 8
• B. 10
• C. 12
• D. 14

Hint:

In close-packed structures, such as FCC and HCP, the coordination number is 12.

Answer 1

The Correct Option is C

In a Hexagonal Close-Packed (hcp) structure, the coordination number is 12. This is because each atom in the hcp arrangement is surrounded by 12 neighboring atoms. Specifically, 6 atoms are arranged in a plane around a central atom, and 3 atoms are positioned above and 3 atoms are positioned below the central atom, making a total of 12 nearest neighbors. This is a characteristic feature of hcp structures, where the packing is highly efficient, and the atoms are arranged in a way that maximizes the number of nearest neighbors.