Question

Statement: Tetrahedral voids and octahedral voids, both are found in hcp and simple cubic structure.
State whether the given statement is true or false.
(A) True
(B) False

Answer 1

To find the solution for the question we should discuss in detail closed packed structures like hcp, ccp, and fcc. Tetrahedral voids are voids that are surrounded by four spheres and present in the corner of a regular tetrahedral and octahedral voids are formed when six spheres present in the layers are placed in the corners of the octahedron.

Complete step-by-step answer: In the question it is asked to comment on the given statement, to verify the given statement is true or false.
So before coming to a conclusion we have to discuss in detail hcp and simple cubic structure, so that we get the idea of the arrangement of the atoms in each close packing and consider various elements in the close packing.
First, let us discuss hcp ie hexagonal close packing. In hexagonal close packing, the atoms are arranged in alternative layers similar to abab fashion.
The atoms are arranged in a hexagonal shape with one additional atom at its center.
Another layer of the atom is arranged in such a way that the atoms of this layer are sandwiched between the top and bottom layers of the atom.
And the atom occupies the tetrahedral voids caused by the top and bottom layers. So in hcp, there are tetrahedral voids, and when two tetrahedral voids of the two layers combine it forms octahedral voids and both the octahedral and tetrahedral voids are present in hexagonal close packing.
In simple cubic close packing the first layers of atoms are placed and the second layer of the atoms are placed exactly as the first layer and this type of arrangement is called square packing and in a square packing only octahedral voids are formed. So in simple cubic packing, only octahedral voids are present.

Therefore the given statement is false.

Note: The hexagonal close packing is a three-dimensional stacking of atoms and the simple cubic lattice is two-dimensional stacking.
In hcp there will be 2n tetrahedral voids per cell and n octahedral voids per cell and n is the number of atoms. The hcp is the one of the efficient close-packed structures which has a packing density of about 74%.