# A solid compound XY has NaCI structure. If the radius of the cation is 100 pm, the radius of the anion $\left ( Y^{-} \right )$ will be: Option 1) 275.1 pm Option 2) 322.5 pm Option 3) 241.5 pm Option 4) 165.7 pm

D Divya Saini

As learnt in

Relation between radius of constituent particle, R and edge length, a for body centered cubic unit cell -

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In a BCC lattice, the oppositely charged ion occupies the centre while the corners are occupied by other ions. So, the distance between the centre and the corner,  $d= \frac{\sqrt{3}a}{2}$

$= \frac{\sqrt{3}}{2} \times 387 pm$

$= 335.151 pm \sim 335 pm$

Option 1)

275.1 pm

This option is incorrect

Option 2)

322.5 pm

This option is incorrect

Option 3)

241.5 pm

This option is correct

Option 4)

165.7 pm

This option is incorrect

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