Due to Frenkel defect, the density of the ionic solids?

Appeared in: KPSC Staff Nurse - 2016

Explanation

A Frenkel defect is a type of point defect in a crystal lattice where an ion leaves its original site and occupies a nearby empty interstitial site.
This creates a pair of defects: a vacancy at the original lattice site and an interstitial defect at the new location.
Crucially, no atoms or ions are lost from the crystal. The total mass of the solid remains constant.
The change in the crystal's volume due to this internal rearrangement of an ion is negligible.
Since density is the ratio of mass to volume, and both remain essentially unchanged, the density of the solid does not change.

Option A: Density decreases in the case of a Schottky defect, not a Frenkel defect.
Option B: Density does not increase because no extra mass is added to the crystal, nor does the volume significantly decrease.
Option D: This option is vague and incorrect. The effect of a Frenkel defect on density is well-defined and predictable; it does not change.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Effect of Frenkel defect on the density of ionic solids as background academic context rather than a clinical decision trigger.
While this is a fundamental chemistry concept, it has relevance in material science, which impacts medicine.
The properties of bioceramics used in dental and orthopedic implants (like zirconia or alumina) are influenced by their crystal structure and defects. These defects can affect the material's strength, longevity, and biocompatibility.
Understanding how defects alter material properties is crucial for designing safe and effective medical devices.

How to Approach the Question

First, identify the key term in the question: 'Frenkel defect'.
Recall the definition of a Frenkel defect: an ion is displaced from its lattice site to an interstitial site within the same crystal.
Analyze the effect on the components of density (Mass and Volume).
Mass: Ask yourself, 'Are any atoms leaving the crystal?' In a Frenkel defect, the answer is no. So, mass is constant.
Volume: Ask, 'Does the crystal expand or shrink significantly?' Since the ion just moves to a nearby empty space, the overall volume change is negligible. So, volume is constant.
Apply the formula for density: Density = Mass / Volume. If both mass and volume are constant, the density must also be constant.

Concept Tested & Keywords

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Practise the full KPSC Staff Nurse - 2016

Attempt every question from this paper in a timed mock, then review the full solution for each one.