The CORRECT statement for cubic close packed (ccp) three-dimensional structure is (are)A. The number of neighbours of an atom present in the topmost layer is 12B. The efficiency of the atom packing is 74%C. The number of octahedral and tetrahedral voids per atom are 1 and 2 respectivelyD. The unit cell edge length is `2sqrt2` times the radius of the atom

The CORRECT statement for cubic close packed (ccp) three-dimensional s

1.	The CORRECT statement for cubic close packed (ccp) three-dimensional structure is (are)A. The number of neighbours of an atom present in the topmost layer is 12B. The efficiency of the atom packing is 74%C. The number of octahedral and tetrahedral voids per atom are 1 and 2 respectivelyD. The unit cell edge length is `2sqrt2` times the radius of the atom
Answer» Correct Answer - B,C,D (a) is incorrect because for any atom in the top most layer, coordination number is not 12 as there is no layer above the topmost layer. (b ) is a known fact. (c ) is correct because in ccp (fcc), number of atoms per unit cell is 4. hence , octahedral voids =4 and tetrahedral voids=8. Therefore , number of octahedral voids per atom =1 and number of tetrahedral voids per atom =2. (d)For ccp (fcc), `r=a/(2sqrt2)` or `a=2sqrt2r`

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