Chemistry Solids MDCAT 2010
PMDC Verified Question 54 of 54
The coordination number of \( \text{Na}^+ \) in \( \text{NaCl} \) crystal is:
A
8
B
4
C
2
D
6
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: 6
Concept:
The coordination number is defined as the number of oppositely charged ions immediately surrounding a specific ion in a crystal lattice.

Solution:
  • In the face-centered cubic (FCC) lattice structure of \( \text{NaCl} \), each \( \text{Na}^+ \) ion is octahedrally surrounded by six \( \text{Cl}^- \) ions.
  • Similarly, each \( \text{Cl}^- \) ion is surrounded by six \( \text{Na}^+ \) ions.
  • Therefore, the coordination number for both ions is 6.


Why other options are incorrect:
  • A, B, C: These numbers do not correspond to the 6:6 octahedral geometry characteristic of the sodium chloride crystal lattice.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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