Question

In Corundum, oxide ions are arranged in hcp arrangement and aluminium ions occupy two third of the octahedral holes. Its formula is .........

(A) Al₂O₃

(B) Al₂O₄

(C) Al₂O₂

(D) AlO₂

Answer 1

Correct answer is: (A) Al₂O₃

There is one octahedral hole per oxide ion and only\(\left(\cfrac{2}{3}\right)^{rd}\)of these holes are occupied.

\(\therefore\) the ratio should be \(\cfrac{2}{3}:1\)= 2 : 3