Question

An ionic solid a+b- crystallizes as a bcc structure the distance between cation and anion in the lattice is 338pm calculate the edge length of unit cell

Answer 1

An ionic solid $a^+b^-$ crystallizes as a bcc structure.

the distance between cation , a^+ and anion, b^- in the lattice is 338pm.

i.e., $a^++b^-=338pm$

from body centered cubic lattice ,

diagonal of cube = $2a^++2b^-$

or, $\sqrt{3}l=2a^++2b^-$

where l is length of unit cell.

or, √3 × l = 2 × 338 pm

or, l = 2 × 338/√3 = 390.3 pm

hence, length of unit cell is 390.3 pm