Class 12th "SOLID STATE"

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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. 
           M = Molar mass.
           NA = Avagadro constant. 
            a   = edge length of unit cell. 



                     Thankyou ! 

                 
             
            

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