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Question: Answered & Verified by Expert
The radius of a calcium ion is $94 \mathrm{pm}$ and of the oxide ion is $146 \mathrm{pm}$. The possible crystal structure of calcium oxide will be
ChemistrySolid StateJEE MainJEE Main 2012 (12 May Online)
Options:
  • A
    tetrahedral
  • B
    trigonal
  • C
    octahedral
  • D
    pyramidal
Solution:
2766 Upvotes Verified Answer
The correct answer is:
octahedral
As per formula,
$$
\begin{aligned}
\text { radius ratio } & =\frac{\text { radius of cation }}{\text { radius of anion }} \\
& =\frac{94}{146}=0.643
\end{aligned}
$$
Since the value is between $0.414-0.732$ hence the coordination no. will be 6 and geometry will be octahedral.

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