Question

For an ionic crystal of general formula $AX$ and coordinate number $6$, the value of radius ratio will be

• A. greater than $0.73$
• B. in between $0.73$ and $0.40$
• C. in between $0.41$ and $0.22$
• D. less than $0.22$

Answer 1

The correct option is B in between $0.73$ and $0.40$

For an ionic crystal of general formula AX and coordinate number 6, the value of radius ratio will be in between 0.73 and 0.414 which corresponds to octahedral coordination.
Note:
Radius ratio greater than 0.73 corresponds to cubic hole.
Radius ratio in between 0.414 and 0.225 corresponds to tetrahedral hole.
Radius ratio in between 0.225 and 0.155 corresponds to planar triangular hole.