Question

The radius of a divalent cation $A^{2+}$ is $94pm$ and that of a divalent anion $B^{2-}$ is $146pm$. The compound $AB$ has:

• A. Rock salt structure
• B. Zinc blende structure
• C. Antifluorite structure
• D. Caesium chloride like structure

Answer 1

The correct option is A Rock salt structure

Radius ratio of ionic compounds helps in determining the structure of compounds.


$\text{Radius of cation,}{r}^{+}=94pm$
$\text{Radius of anion,}{r}^{-}=146pm$
Radius ratio,
$\frac{r^{+}}{r^{-}}=\frac{94}{146}=0.64$
It is in the range of $0.414-0.732,$ which represent octahedral type of structure.
Thus, it has the coordination number of 6.
Rock salt has the octahedral type of structure.
Hence, correct option is Rock salt structrue.