Chemistry Solids DUHS 2023
PMDC Verified Question 24 of 54
Which of the following is a covalent crystal?
A
\( \text{NaCl} \)
B
\( \text{KI} \)
C
\( \text{MgBr}_2 \)
D
Diamond
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Diamond
Concept:
Covalent crystals (network solids) consist of atoms connected by a continuous, giant network of covalent bonds.

Solution:
  • Diamond is composed entirely of carbon atoms.
  • Every carbon atom is covalently bonded to four others in a rigid, 3D tetrahedral geometry.
  • Because there are no discrete molecules or ions, and the entire structure is one massive covalent molecule, diamond is a quintessential covalent crystal.


Why other options are incorrect:
  • A, B, C: \( \text{NaCl} \), \( \text{KI} \), and \( \text{MgBr}_2 \) are formed by a metal and a non-metal, creating lattices held together by electrostatic forces between cations and anions. These are ionic crystals.

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