Question

The number of tetrahedral and octahedral voids in CCP unit cells are respectively.
(A) 4, 8
(B) 8, 4
(C) 12, 6
(D) 6, 12

Answer 1

In CCP or fee structure Number of lattice points Z. Number of tetrahedral voids is equal to two times the number of octahedral voids. By using these formulas we can easily calculate the number of tetrahedral and octahedral voids.

Complete answer:
Tetrahedral void may be a simple triangular void during a crystal and is surrounded by 4 spheres arranged tetrahedrally around it.
On the opposite hand, an octahedral void may be a twice triangular void with 1 triangle vertex upwards and therefore the other triangle vertex downwards and is surrounded by 6 spheres.
there are many differences such as :-
Crystal System-Tetrahedral Voids are often found in substances having a tetrahedral arrangement in their crystal system. Octahedral Voids are often found in substances having an octahedral arrangement in their crystal system.
Location within the unit-Tetrahedral Voids are often observed in edges of the unit .Octahedral voids are often observed within the centre of the unit .
Coordination Number-The coordination number of the tetrahedral void is 4.
The coordination number of the octahedral void is 6.
Number of Voids -Within the space lattice there are two tetrahedral voids per sphere within the space lattice .
Hence the correct answer is Option C.

Note: If the number of atoms in ccp is n then number of tetrahedral voids is 2n . Number of octahedral voids is n. Therefore, in the given question, the number of atoms is equal to the number of octahedral voids that is 4 and the number of tetrahedral voids are 8.