The edge length of a face-centred cubic unit cell is `508 pm`. If the radius of the cation is `110 pm` the radius of the anion is

Options

A. 288 pm
B. 398 pm
C. 154 pm
D. 618 pm

Answer

C

Explanation

For centred unit cell,
`2(r^(+)+r^(-))=a`
`r^(+)-"radii of cation"`
`r^(-)="radii of anion"`
`2(1000+r^(-))=508`
`100+r^(-)=(508)/(2)`
`r^(-)=(508)/(2)-100`
`=254-100=154" pm"`