The mineral haematite, ` Fe_(2)O_(3)` consists of a cubic close packed array of oxide ions with `Fe^(3+)` ions occupying intersitial positions. Predict whether the iron ions are in the octahdral or tetrahedral holes. Radius of ` Fe^(3+)` = 0.65Å .

Explanation

`r_+ //r_` =0.65 Å/ 1.45 Å which lies in the range 0.414-0.732 . Hence , `Fe^(3+)` ions will be in the octahedral holes.