1.

Give the types of close packing of constituent particles.

Answer»

various types of close packing of constituent particles. 

Close packing in three dimensions

Simple Cubic Lattice or Structure:

  • AAA….type arrangement generates simple cubic lattice in three dimension 
  • Its unit cell is primitive cubic unit cell. 
  • Packing efficiency = 52.4% 

Hexagonal Close Packing Structure (HCP): 

  • ABAB….Type arrangement 
  • Example: Mg, Zn. 
  • Packing efficiency = 74% o Coordination number = 12 
  • It has N no of octahedral voids and 2N no. of tetrahedral voids if it has N no. of spheres.

Cubic Close Packing Structure (CCP): 

  • ABCABC….Type arrangement 
  • CCP structure is also called FCC structure. Example: Ag, Cu. 
  • Packing efficiency = 74% 
  • Coordination number = 12.
  • If there is N no. of close packed spheres then it has 2N no. of tetrahedral voids and N no. of octahedral voids. 


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