(i) Radius of the cations just filling into the tetrahedral hole
= Radius of the tetrahedral hole
= 0.225 × 195 = 43.875 pm
(ii) For cation A+ with radius = 82 pm
As it lies in the range 0.414 – 0.732, hence the cation A+ can be slipped into the octahedral hole of the crystal A+ Br-.