Q)
The mineral haematite, $Fe_2O_3$ consists of a cubic close packed array of oxide ions with $Fe^{3+}$ ions occupying interstitial positions. Predict whether the iron ions are in the octahedral or tetrahedral holes. Radius of $Fe^{3+} = 0.65 A^{\large\circ}$ and that of $O^{2-} = 1.45A^{\large\circ}$.
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