1.19 Ferric oxide crystallises in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide.
Let the number of oxides (O2−) ions be x. So, the number of octahedral voids = x It is given that two out of every three octahedral holes are occupied by ferric ions. So, number of ferric (Fe3+) ions
Therefore, the ratio of the number of Fe3+ ions to the number of O2− ions,
