Question

What is the ideal radius ratio for octahedral arrangement?

Answer 1

1. The ideal radius ratio for an octahedral arrangement is the ratio of the radius of the cation (r₊) to the radius of the anion (r₋) that allows the cation to fit perfectly into the octahedral void without distorting the crystal structure.
2. This ideal radius ratio is given by
   `(r_+)/(r_-) = 0.414`
3. This ratio ensures that the cation is large enough to touch the surrounding anions, providing maximum stability to the structure.
4. If the radius ratio is less than 0.414, the cation is too small and cannot maintain the octahedral arrangement. If it is greater, the coordination number may increase to 8 (cubic coordination).