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# Solid State

## Solid State PDF Notes, Important Questions and Synopsis

SYNOPSIS

• Differences between crystalline solid and amorphous solid:

 Crystalline Solid Amorphous Solid The internal arrangement of particles is well defined. The internal arrangement of particles is not well defined. There is regularity in the external form when crystals are formed. There is no regularity in the external form when amorphous solids are formed. These have a sharp melting point. These melt over a range of temperatures. These have characteristic heat of fusion. These do not have characteristic heat of fusion. Crystalline solids give a regular cut when cut with a sharp-edged knife. Amorphous solids give an irregular cut. Crystalline solids are regarded as true solids. Amorphous solids are super-cooled liquids or pseudo solids. These are generally incompressible. These may be compressed to an extent.
• Classification of crystals into seven systems:

 Crystal system Unit cell dimensions and angles Bravais Examples Lattices Cubic a = b = c; α= β= γ= 90° SC, BCC, FCC NaCl Orthorhombic a ≠b ≠c; α= β= γ= 90° SC, BCC, end centred & FCC SR (Rhombic sulphur) Tetragonal a = b ≠c; α= β= γ= 90° SC, BCC Sn, ZnO2 Monoclinic a ≠b ≠c; α= γ= 90°≠β SC, end centred SM (Monoclinic sulphur) Rhombohedral a = b = c; α= β= γ = 90° SC Quartz Triclinic a ≠b ≠c; α≠β≠γ≠90° SC H3BO3 Hexagonal a = b ≠c; α= β= 90°;γ= 120° SC Graphite
• Analysis of cubical system:

 Property SC BCC FCC Atomic radius (r) a = edge length No. of atoms per unit cell (Z) 1 2 4 C. No. 6 8 12 Packing efficiency 52% 68% 74% No. of voids (a) octahedral (Z) (b) tetrahedral (2Z) - - - - 4 8

• Neighbourhood of a particle:
1. Simple cubic (SC) structure:

 Type of neighbour Distance No. of neighbours nearest a 6 (shared by 4 cubes) (next)1 12 (shared by 2 cubes) (next)2 8 (unshared)
2. Body-centred cubic (BCC) structure:

 Type of neighbour Distance No. of neighbours nearest 8 (next)1 =a 6 (next)2 12 (next)3 24 (next)4 8
3. Face-centred cubic (FCC) structure:

 Type of neighbour Distance No. of neighbours nearest (next)1 a (next)2 24 (next)3 12 (next)4 24

Packing of constituents in crystals:

 Structure Packing                           pattern Coordination number Packing efficiency (%) Unit cell Simple cubic AAAA 6 52 Primitive cubic Body-centred cubic or BCC ABAB 8 68 Body-centred cubic Hexagonal closed packing ABAB 12 74 Non-cubic Cubic closest packing or FCC ABCABC 12 74 Face-centred cubic
• Ionic crystals:

 C. No. Limiting radius ratio 3 0.155 - 0.225 (triangular) 4 0.225 - 0.414 (tetrahedral) 6 0.414 - 0.732 (octahedral) 8 0.732 - 0.999 (cubic)
• Crystal defects (Imperfections):

• Stoichiometric effect:
• Schottky defect:

Frenkel defect:
• This defect is created when an ion leaves its correct lattice site and occupies an interstitial site. Examples: ZnS, AgCl, AgBr, AgI

Non-stoichiometric effect:

Metal excess defect:

• These defects arise due to anionic vacancies.
• This type of defect is exhibited by alkali halides. Examples: NaCl, KCl

Metal deficiency defect:

• These defects arise when a compound has metal deficiency due to the absence of a metal ion from its lattice site.
• This type of defect is generally found in compounds of transition metals. Examples: ZnO, CdS

JEE Main - Chemistry
Asked by sohamsaha321 | 18 May, 2022, 02:20: PM