Deep-Dive Guides · Solid State — Structures
Solid State: Lattices, Close Packing, Ionic Structures, Lattice Energy & Defects
The organising idea: lattice geometry → packing & holes → which structure an ionic solid adopts → its thermodynamics (lattice energy), defects and electronic/magnetic properties. Everything below hangs on that one chain of logic.
Free extract — the opening section of the guide, in full.
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Solid-state questions in CSIR-NET are almost always a chain: you are given (or must decide) the packing type and which holes are filled, and everything else follows — coordination numbers, formula (Z), density, lattice energy trend, and even defect/conductivity behaviour. Learn the logic, not 20 disconnected structures.
| Step (input) | What you decide/compute | Output that feeds the next step |
|---|---|---|
| Lattice + basis | Crystal system, Bravais type, unit cell | Symmetry, systematic absences (which reflections appear) |
| Close packing (hcp/ccp) | Packing efficiency, number & type of voids | Available sites: N octahedral + 2N tetrahedral holes |
| Radius ratio r₊/r₋ | Predicted coordination number & hole type | Which holes the cation occupies |
| "Fill the holes" | The named structure (NaCl, ZnS, CaF₂…) | CN of both ions, formula units Z per cell |
| Z, M, a | Density ρ = Z·M/(NA·a³) | Numeric density; consistency check |
| Charges, r₀, Madelung | Lattice energy U (Born–Landé / Born–Haber) | Stability, m.p. trend, solubility trend |
| Deviations from ideal | Defects (Schottky/Frenkel), doping, bands | Density change, ionic/electronic conductivity, colour, magnetism |
Read the rest of this guide
The remaining 10 sections — Crystal systems, Bravais lattices & Miller indices, Close packing, unit-cell geometry & voids, The radius-ratio rule, Ionic structures — the diagram-heavy core and more — are part of ChemVidya Full Access, along with the other guides, the books, the study notes and 6,000+ practice questions with worked solutions.