Voids in Close Packed Structures — Predicted 2026

AI-Predicted Question Angles for UPSC 2026

Based on trend analysis, current affairs, and recurring themes in Voids in Close Packed Structures.

Complex Stoichiometry with Mixed Void Occupancy

medium

While current NEET questions usually involve one type of void occupancy, a slightly more challenging question could involve two different cations occupying different types or fractions of voids simultaneously. For example, 'In a compound, anions form FCC. Cation A occupies 1/2 of tetrahedral voids, and Cation B occupies 1/4 of octahedral voids. What is the formula?' This tests multiple concepts in one problem, requiring careful calculation for each cation and then combining them.

Relating Void Occupancy to Density Calculations

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A more integrated question could ask students to calculate the density of an ionic compound, where the formula itself needs to be derived from void occupancy. This would combine the concepts of voids, stoichiometry, and density calculations ($ ho = ZM / (a^3 N_A) $). While density calculations are standard, combining it with void occupancy adds an extra layer of complexity, making it a good differentiator for higher ranks.

Spatial Relationship and Distances between Voids/Atoms

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Questions asking for distances between specific void centers, or between a void center and an atom center, are becoming more common as NEET aims to test deeper spatial reasoning. The example MCQ provided in this document (distance between OV and TV) is a prime example. This requires a strong understanding of fractional coordinates and 3D geometry within the unit cell, moving beyond simple counting of voids.