what is the formula of a compound in which element P forms ccp lattice and atoms of Q occupy 2/3rd of tetrahedral voids ?

Answer

`Q_4P_3`

Explanation

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`