JEE Advanced 2016 · Paper 2 · Chemistry Q27

ChemistryMultiple correct+4 / -2Question 27 of 54

The CORRECT statement(s) for cubic close packed (ccp) three dimensional structure is(are)

The number of the nearest neighbours of an atom present in the topmost layer is 12

The efficiency of atom packing is 74%

The number of octahedral and tetrahedral voids per atom are 1 and 2, respectively

The unit cell edge length is

2\sqrt2

times the radius of the atom

Answer and worked solution

Official answer: B, C, D

(A) An atom in the topmost layer has 6 neighbours in its layer and 3 below: 9, not 12. False.
(B) ccp packing efficiency is 74%. True.
(C) Per atom there is 1 octahedral void and 2 tetrahedral voids. True.
(D) Atoms touch along the face diagonal: $\sqrt2a=4r$ , so $a=2\sqrt2r$ . True.

(B), (C), (D)

Topics:Packing efficiency Crystal lattices and unit cells

JEE Advanced 2016 · Paper 2, Chemistry question 27