The edge length of an FCC lattice of an ionic substance is . If the radius of the cation is , the ra — Solid State Chemistry Question

💡 Solution & Explanation

For the FCC-type closest contact along the face diagonal, $4r = \sqrt{2}a$ for equal-radius contact distance expressed through the effective nearest-neighbour sum, so $r_+ + r_- = \frac{a}{2}=254\text{ pm}$. Therefore $r_- =254-110=144\text{ pm}$.