Chemistry Solids MDCAT 2013
PMDC Verified Question 53 of 54
In the structure of \( \text{NaCl} \), each sodium ion is surrounded by chloride ions:
A
4
B
6
C
5
D
8
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 6
Concept:
Ionic crystals arrange themselves in a lattice that maximizes electrostatic attraction and minimizes repulsion, dictating specific coordination numbers.

Solution:
  • \( \text{NaCl} \) crystallizes in a face-centered cubic (FCC) structure.
  • In this specific arrangement, every single \( \text{Na}^+ \) cation sits in an octahedral hole created by the \( \text{Cl}^- \) anions.
  • This geometry inherently dictates that exactly 6 chloride ions surround each sodium ion.


Why other options are incorrect:
  • A, C, D: 4 (tetrahedral) and 8 (cubic) are coordination numbers for different lattice types (like \( \text{ZnS} \) or \( \text{CsCl} \)), not \( \text{NaCl} \).

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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