A solid A+B- has the B- ions arranged as below. If the A+ ions accupy half of the tetrahedral sites in the structure. The formula of solid is:
In a closed packed structure, the number of tetrahedral voids per atom of the crystal is two. Since, half of the tetrahedral voids are occupied by A+, the number of A+ is same as that of B- in the crystal. Thus, formula is AB. Or
No. of B- ions in until cell =
A+ ions occupies 50 of tetrahedral voids =
The ratio of B- and A+ is 1:1