Question

The coordination number for an octahedral site in pure copper is .........

• A. 4
• B. 6
• C. 8
• D. 12

Hint:

In FCC structures, the coordination number for an octahedral site is 6, while for a tetrahedral site, it is 4. This distinction is important when analyzing atomic arrangements in different crystal structures.

Answer 1

The Correct Option is B

In crystal structures, the coordination number refers to the number of nearest neighbors surrounding a central atom or ion. For pure copper, which adopts a face-centered cubic (FCC) crystal structure, the coordination number for an octahedral site is 6. This is because, in the FCC structure, each atom is surrounded by six atoms at an equal distance in an octahedral arrangement. 
Step 1: Understanding the options 
- Option (A): 4 — This is the coordination number for a tetrahedral site, not an octahedral site. 
- Option (B): 6 — Correct. In the FCC structure, the coordination number for an octahedral site is 6. 
- Option (C): 8 — This corresponds to the coordination number for a cubic site, which is not correct for the octahedral site in FCC copper. 
- Option (D): 12 — This is the coordination number for an atom in a close-packed structure, but not for an octahedral site. 
Step 2: Conclusion The correct coordination number for an octahedral site in pure copper is 6, making Option B the correct answer.