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

Options

A. a. The edge length of unit cell is 4.2 Å
B. b. The coordination number for `Cs^(o+)` is 6
C. c. CsBr has bcc-type structure
D. d. `Br^(Θ)` ions touch each other along the edge

Answer

A, C, D

Explanation

`(r_(Cs^(o+)))/(r_(Br^(Θ)))=(1.69)/(1.95)=0.867` (bcc structure)
Hence, `Cs^(o+)` ion lies at the "body centre of cubic void" where CN of `Cs^(o+)=8`.
BsBr has bcc structure with `Br^(Θ)` forming simple cubic lattice and `Cs^(o+)` ion in the void (at body centre). for bcc, `(2r_(Cs^(o+))+r_(Br^(Θ)))=sqrt(3)a`
`2(1.69+1.95)=sqrt(3)a implies a=4.2` Å