Question

The radius of a calcium ion is $94pm$ and of an oxide ion is $146pm$. Predict the crystal structure of calcium oxide ?

• A. $NaCl$ type
• B. $ZnS$ type
• C. $N{a}_{2}O$ type
• D. $ZnC{l}_2$ type

Answer 1

Answer: (A)

$NaCl$ type

$\frac{r^{+}}{r^{-}}$ ratio is constant for a ionic crystal structure,

so $\frac{r^{+}}{r^{-}}=\frac{94}{146}=0.64$

It is between 0.414 to 0.732

so it same as $CCP$, like in NaCl.