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DEFECTS IN SOLIDS "Any departure from the perfectly ordered arrangement in a crystal is termed as defects in that crystal."  These are two types of defects in solids or crystals : (i)  Electronic defects : The electrons and holes in solids gives rise to electronic defects.  "The error in charge distribution in solids is called electronic defects." •  These defects are produced when the composition of an ionic crystal doesn't correspond to the exact stoichiometric formula. (ii)  Atomic defects : The   defects caused by the non-arrangement of ions/atom. These are two types of atomic defects as follows : [A]  Point Defects : The defects caused by a departure from the periodic arrangement of particles in the vicinity of an atoms.  These are three types of Point Defects : 1.  Stoichiometric Defects.  2.  Non-Stoichiometric Defects.  3.  Impurity Defects.  [B]  Non-Stoichiometric Defects : 1.  Metal excess defect...

PACKING IN CRYSTAL SYSTEM  •  There are two types of Crystal packing as following : •  Hexagonal Closest Packing :  Coordination number = 6  •  Cubic Closest Packing/Square Closest Packing :  Coordination number = 4  Term related to packing systems : 1. Coordination Number : The number of nearest neighbours of a sphere or the number of spheres touching any sphere.  2. Packing efficiency or Packing fraction : The percentage of total space filled by the particles is called packing efficiency.      Formula of packing efficiency : Packing efficiency = [volume of atoms in a unit cell / total volume of a unit cell]×100 •  Density of Unit cells :     [ d = Z × M/NA × a^3 ] Where,               d = density.              Z  = Effective no.of atoms in unit.      ...

CRYSTALS/CRYSTALLINE A constituents are arranged A highly ordered microscopic structure,forming a crystal lattice that extend in all directions.                 Fig. 1 : Crystal CLASSIFICATION OF CRYSTALS : These are four types of crystals are following :  1. Ionic Crystals : It is binding by ionic        bonds.               Fig. 2 : (NaCl)  Properties/characteristics of Ionic Crystals :  •  It is hard and brittle.  • High melting point.  • High heat of fusion.  • Poor thermal and electric                      conductors.  Example : NaCl, PbS. etc.  2. Molecular Crystals :   It is binding            by  Vander waal's forces ( London dispersion, dipole-dipole force, hydrogen bonds).    ...

ANISOTRPOPY It is the property of substance to show variations in physical properties along different moleculer axis. It is opposite of isotropic materials " अनिसोट्रॉपी एक सामग्री की संपत्ति है जो इसे अलग-अलग दिशाओं में अलग-अलग गुणों को बदलने या ग्रहण करने की अनुमति देती है जैसा कि आइसोट्रॉपी के विपरीत है। " Example : Which all material/substance who can adjust their size and shape as per requirement.  ALLOTROPES When a substance/matter exists in two or more forms then they call allotropes.  Example : Diamond and graphite are allotropes of carbon.  POLYMORPHISM When a single substance crystallized in two or more forms under different conditions of solidification is called polymorphism and the crystal showing polymorphism are called polymorphous .   Example : Silica forms many polymorphous such as alpha, bita- quartz, tridimite, crystobatic, coesite.  ISOMORPHISM Iso = Same or identical Morph = Shape or Forms When...