Question

A compound $XY$ crystallizes in bcc lattice with unit cell edge length of $480$ pm. If the radius of $Y$ is $225$ pm, then the radius of $X^{+}$ is:

• A. $190.70$ pm
• B. $225$ pm
• C. $127$ pm
• D. none of the above

Answer 1

The correct option is A $190.70$ pm

For a B.C.C Ionic crystal

$r^{+}+r^{-}=\frac{\sqrt{3}a}{2}$

we have, $a=480pm$ and $r^{-}=225pm$

Therefore,

$r_x^{+}+225=\frac{1.732\times 480}{2}$

Hence the answer is $r_x^{+}=190.7$.