Question

Which of the following oxides have rock salt structure with coordination number $6:6$?

• A. $BeO$
• B. $MgO$
• C. $CaO$
• D. $SrO$

Answer 1

Answer: (B), (C), (D)

$CaO$
$MgO$
$SrO$

Option $\left(D\right)$ is correct.

$MgO,CaO$ and $SrO$ have rock salt structure with coordination number 6:6. In these compounds $X^{2-}$ ions in ccp $Y^{2+}$ ions occupy all octahedral voids.

$BeO$ has wurtzite type structure with coordination number 4:4.In it $O^{2-}$ ions in hcp $B{e}^{2+}$ ion occupy alternate tetrahedral voids