In corundum, oxide ions are arranged in hexagonal close packing and aluminium ions occupy two-third of the octahedral voids. What is the formula of corundum ?

In corundum, oxide ions are arranged in hexagonal close packing and al

1.	In corundum, oxide ions are arranged in hexagonal close packing and aluminium ions occupy two-third of the octahedral voids. What is the formula of corundum ?
Answer» SOLUTION :Suppose oxide ions =n. Then octahedral voids= n. HENCE, `Al^(3+)` ions `=2/3xxn="2n"/3` `therefore` Ratio `Al^(3+) : O^(2-)="2n"/3:n =2:3` , i.e., FORMULA is `Al_2O_3`