NH4Cl crystallizes in a body-centered cubic lattice with an edge length of unit cell equal to 387 pm. If the radius of the Cl− ion is 181 pm, the radius for NH+4 ion is?
154.1 pm
For bcc lattice, 2rNH+4+2rCl−=a√3
(NH+4 ion lies in the cubic void Cl− ions)
Or, rNH+4+rCl−=a√32=387×1.7322=335.1
Or rCl−=335.1−101.0=154.1pm