Question

An ionic solid $A^{\oplus }{B}^{⊝}$ crystallizes as a bcc structure. The distance between cation and anion in the lattice is $338$ pm. The edge length (in pm) of the unit cell is :

• A. $338.2$
• B. $390.3$
• C. $292.7$
• D. $507.0$

Answer 1

Answer: (B)

$390.3$

Given that $r_{+}+r_{-}=338$
In a BCC lattice $2(r_{+}+r_{-})=a\sqrt{3}$
$a=390.3\text{pm}$