A solid `AB` has `CsCl`-type structure. The edge length of the unit cell is `404` pm. Calculate the distance of closest approach between `A^(o+)` and `B^(Θ)` ions.

Options

A. `4.0A^(0)`
B. `6.4A^(0)`
C. `3.5A^(0)`
D. `7.0A^(0)`

Answer

3

Explanation

(A) Simple cubic and FC C have a=b=c, `alpha=beta=gamma=90^(@)` and belong to the same crystal system (cubic).
(B) Cubic `(a=b=c,alpha=beta=gamma=90^(@))`
Thombohedral `(a=b=c,alpha=beta=gammacancel=90^(@))`.
These are two different crystal systems.
(C) Cubic and tetragonal are two different crystal systems.
(D) Hexagonal: `alpha=beta=90^(@)(gamma=120^(@))` Monoclinic : `alpha=gamma=90^(@)cancel=beta`, i.e., each has two crystallographic angles of `90^(@)`. Further, these are two different crystal systems.