Answer:
The fraction of the available octahedral positions are filled with 
ions is 
Explanation:
If there are n numbers of spheres in HCP in packing:
Number of octahedral void = n
Number of tetrahedral void = 2n
Total number of voids = n + 2n = 3n
The 
crystal structure consists of an HCP arrangement of 
ions.
Number of spheres in HCP = 6
Number of = 6
Number of octahedral voids = 6
Number of tetrahedral void = 12
Number of aluminum ions when there are 6 ion =
Number of voids in which 
ions are present = 4
The fraction of the available octahedral positions are filled with ions = 
I believe the answer is 8
Endothermic reactions are reactions that proceed by the absorption of heat (energy) while exothermic reactions involve a release of energy.
a) Formation of frost on a car window in winter is an exothermic process as heat is liberated when liquid water freezes to form crystals
b) Formation of water condensate on a glass of ice water is an endothermic reaction since heat is absorbed by the cold water from the glass container thereby cooling it.
c) A decrease in the temperature as ammonium nitrate is added to water is an endothermic reaction
There is one atom in a Monoatomic Ion whereas Many in Polyatomic.
It's simple!!! you're Welcome:)
