`CsCl` crystallizes in body centred cubic lattice .If `'a'` is its edge length then which of the following expression is correct?

Options

A. `r_(CS^(+))+r_(Cl^(-))=sqrt(3)/(2)a`
B. `r_(CS^(+))+r_(Cl^(-))=sqrt(3)a`
C. `r_(CS^(+))+r_(Cl^(-))=3a`
D. `r_(CS^(+))+r_(Cl^(-))=(3a)/(2)`

Answer

1

Explanation

In the bcc unit cell of `CsCl`, we have the `Cs^(+)` (at the centre) in touch with the two `Cl^(-)` ions diagonally arranged thus
`2r_(Cs^(+))+2r_(Cl^(-))=sqrt(3)a`
or `r_(Cs^+)+r_(Cl^-)=sqrt(3)/(2)a`