Q. The limiting radius ratio for tetrahedral shape is
AMUAMU 2005
Solution:
Limiting radius ratio The ratio of the radius of cation $ (r^{+}) $ to that of anion $ (r^{-}) $ is known as limiting radius ratio. It plays an important role in the crystal structure of ionic substance.
Limiting radius ratio $\left(\frac{r^+}{r^-}\right)$
Shape
Coordination number
Example
1. $0.115 - 0.225$
Plane trigonal
3
Boron oxide
2.$0.225 - 0.414$
Tetrahedral
4
$ZnS$
3.$ 0.414 - 0.732$
Square planar
4
-
4.$0.414 - 0.732$
Octahedral
6
$AgCl, MgO, NaBr$
4.$0.732- 1.00$
Cubic
8
$CsCl, CsBr$
| Limiting radius ratio $\left(\frac{r^+}{r^-}\right)$ | Shape | Coordination number | Example |
|---|---|---|---|
| 1. $0.115 - 0.225$ | Plane trigonal | 3 | Boron oxide |
| 2.$0.225 - 0.414$ | Tetrahedral | 4 | $ZnS$ |
| 3.$ 0.414 - 0.732$ | Square planar | 4 | - |
| 4.$0.414 - 0.732$ | Octahedral | 6 | $AgCl, MgO, NaBr$ |
| 4.$0.732- 1.00$ | Cubic | 8 | $CsCl, CsBr$ |