How will you distinguish between the following pairs of terms?
a. Hexagonal close-packing and cubic close-packing
b. Crystal lattice and unit cell
c. Tetrahedral void octahedral void

Explanation

(a) In hexagonal close packing (hcp), the shperes of the third layer are vertically above the spheres of the first layer (ABABAB…..type). On the other hand , in cubic close packing (ccp), the shperes of the fourth layer are present above the spheres of the first layer (ABCABC.....type).