Solid State - JEE Advanced Previous Year Questions with Solutions

Solid State typically contributes 1–2 questions per year in JEE Advanced, worth 4–8 marks. While that may seem small, these questions are highly predictable in topic (defects, packing, unit cell density) and often appear as high-scoring integer or multi-correct types where thorough preparation almost guarantees full marks.

Crystal defects (especially Frenkel vs. Schottky distinctions and F-centres), packing efficiency of 2D and 3D unit cells, CCP structure properties, and density calculations for FCC unit cells are the most frequently tested topics. Together they account for roughly 80% of all Solid State questions asked between 2009 and 2023.

NCERT Class 12 Chemistry Chapter 1 is the necessary foundation, but it is not sufficient on its own for JEE Advanced. NCERT covers definitions and basic formulas. JEE Advanced questions require you to apply those concepts in multi-step problems — for example, transforming an NaCl unit cell through four operations and counting atoms at each stage, as seen in the 2017 paper.

For a 2D square unit cell where atoms touch along the edge (edge length a = 2r): calculate the area of atoms inside the cell divided by the total area of the cell. For the arrangement in JEE 2010, this gives 2πr² / 4r² × 100 = 78.54%. Always identify how many atoms belong to the cell before applying the formula.

An atom in the topmost layer of a CCP structure has 9 nearest neighbours: 6 in the same layer and 3 in the layer directly below it. This is different from an atom in an interior (bulk) layer, which has 12 nearest neighbours. JEE Advanced 2016 specifically tested this distinction in its multi-correct question.