JEE Advanced levelOne or more correct optionsDifficulty 3 of 3ss129
Which statements comparing hcp and ccp arrangements of identical spheres are correct?
ABoth have a coordination number of 12.
BIn ccp the close packed layers are perpendicular to the body diagonal of the fcc cell.
CIn both, the ratio of tetrahedral to octahedral voids is 2:1.
DThe packing efficiency of hcp (about 74%) is higher than that of ccp (about 68%).
Answer: A, B, C
Both have CN 12 and efficiency 74%, and both give N octahedral and 2N tetrahedral voids for N atoms. The layers of ccp are the (111) planes, perpendicular to the body diagonal. D is wrong because the two efficiencies are equal.