Question

In a AB unit cell (Rock salt type) assuming `A^(+)` forming fcc :
A. The nearest neighbout of `A^(+)` is `6B^(-)` ion
B. The nearest neighbour of `B^(-)` is `6A^(+)` ion
C. The nearest neighbour of `B^(-)` is `6A^(+)` ion
D. The packing fraction of AB crystal is `(sqrt(3)pi)/(8)`

Answer 1

Correct Answer - A::B::C
In AB which in NaCl type crystal
(a) Here `A^(+)` is surrounded by 6 `B^(-)` because `A^(+)` is in octahedral void of `B^(-)`. Is in octahedral void of `A^(+)`.
(c) The second neighbouring of `A^(+)=12A^(+)` ions
The packing fraction of `A^(+)=sqrt(3)/(8)pi` and not of the whole All crystal. Choice (a) is correct Choice (b) is correct Choice (c) is correct, Choice (d) is incorrect.