Edge length of `M^(+)X^(-)` (fcc structure) is `7.2^(@)A`. Assuming `M^(+)-X^(-)` contact along the cell edge, radius of `X(-)` ion is `(r_(M+)=1.6^(@)A)`:

Options

A. `2.0A^(@)`
B. `5.6A^(@)`
C. `2.8A^(@)`
D. `3.8A^(@)`

Answer

A

Explanation

`2(r_(M^(+))+r_(X^(-)))=7.2`
`2(1.6+r_(X^(-)))=7.2`
`r_(X^(-))=1.0 Å`