If the radious of `Cs^(o+) = 1.69 Å` and `Br^(Θ) = 1.95 Å`, then which of the following is//are correct statement?

Options

A. Edge length of unit cell is 4.2 Å
B. Coordination number for `Cs^(+)` is 8
C. CsBr has BCC type structure
D. `Br^(-)` ions touch each other along

Explanation

`(r_(Cs^(+)))/(r_(Br^(-)))=(1.69)/(1.95)=0.867`
Hence Cs+ lies in the “body centre or cubic void” where co-ordination no. of `Cs^(+)` is 8.
CsBr has BCC type structure with forming simple cubic lattice and in the void. Let edge length of the unit cell = a. We have `sqrt(3a)=2(r_(Cs^(+))+r_(Br^(-)))impliesa=(2)/(sqrt(3))(1.69+1.95)=4.2Å`