Question

Which of the following are true for radius ratio $\left(\frac{r^{+}}{r^{-}}\right)$?

i) If it is between $0.732$ and $0.414$, then the coordination number is $6$ and is octahedral.

ii) If it is above $0.732$ and less than $1.00$, then coordination number is $8$ and is cubic.

iii) If it is between $0.225$ and $0.155$, then coordination number is $3$ and is triangular.

iv) If it is between $0.732$ and $0.878$, then coordination number is $8$ and cubic.

• A. i and ii
  
• B. i and iii
  
• C. i,ii, iii and iv
  
• D. iii,iv
  

Answer 1

The correct option is C i,ii, iii and iv

Radius ratio helps in the determination of arrangement of ions in various types of crystal structures.

If the radius ratio is between 0.414 and 0.732 then the coordination number is 6 and the shape is octahedral.

If the radius ratio is between 0.155 and 0.225 then the coordination number is 3 and the shape is triangular planar.

If the radius ratio is between 0.732 and 1.0000 then the coordination number is 8 and the shape is cubic.

Here all the four options are correct.