JEE Advanced2016ChemistrySolid StateActual
The CORRECT statement(s) for cubic close packed (ccp) three dimensional structure is (are)
Options
- AThe number of the nearest neighbours of an atom present in the topmost layer is 12
- BThe efficiency of atom packing is 74 %
- CThe number of octahedral and tetrahedral voids per atom are 1 and 2, respectively
- DThe unit cell edge length is 2 2 times the radius of the atom
Correct answer
B. The efficiency of atom packing is 74 %
Step-by-step solution
CCP is ABC ABC ..... type packing A] In topmost layer, each atom is in contact with 6 atoms in same layer and 3 atoms below this layer. B] Packing fraction = 4 × 4 3 π r 3 4 r 2 3 = 0.74 C] Each FCC unit has effective no of atoms = 4 Octahedral void = 4 Tetrahedral void = 8 D] 4 r = a 2