Question

$AB$ crystallizes in a body centred cubic lattice with edge length $\left(a\right)$ equal to $387pm.$ The distance between two oppositely charged ions in the lattice is:
(AIPMT - 2010)

• A. $335pm$
• B. $200pm$
• C. $300pm$
• D. $250pm$

Answer 1

The correct option is A $335pm$

For BCC:
Distance between two oppositely charged ions in the lattice is distance between corner and body centre i.e. half the distance of body diagnonal.

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

$\therefore r^{+}+r^{-}=\frac{\sqrt{3}\times 387}{2}pm$

$=335.14pm\approx 335pm$