Question

Choose the correct statement(s) regarding cubic close packing.

• A. Cubic close packing gives fcc structure
• B. Fourth layer is identical to the first layer
• C. Cubic close packing gives bcc structure
• D. Fourth layer is identical to the second layer

Answer 1

Answer: (A), (B)

Fourth layer is identical to the first layer

In ccp arrangement, the second row of spheres is placed in the interstices or depressions of the first-row spheres. The third layer is placed above the second layer covering the octahedral voids of the second layer such that the spheres of the third layer are not aligned with either of first or the second layer. Thus, it gives ABCABC... type of arrangement. This structure is called cubic close packed (ccp).
In ABCABC.... type of arrangement, fourth layer is similar to the first layer. Thus, statement (a) is correct.
Cubic close packing gives fcc struture as shown is diagram below.

Hence, they are also called face centred cubic.
Thus, statement (b) is correct.