Question: 51. Right option for the number of tetrahedral and octahedral voids in hexagonal primitive unit cell are :
(1) 8,4
(2) 6,12
(3) 2,1
(4) 12,6
Answer: Option (4)
Explanation:
In a hexagonal close packed structure, the number of atoms present in one unit cell is 6.
In close packed structures, the number of octahedral voids is equal to the number of atoms present in the unit cell.
Therefore, the number of octahedral voids in a hexagonal unit cell is 6.
The number of tetrahedral voids in a close packed structure is twice the number of atoms present in the unit cell.
Hence, the number of tetrahedral voids is 2 \times 6 = 12.
Thus, the correct number of tetrahedral and octahedral voids in a hexagonal unit cell are 12 and 6 respectively.
Therefore, the correct option is (4).