Question

An ionic compound is made up of A cations and B anions. If A cations are present
at the alternate corners and B anion is present on the body of the diagonal, what is
the formula of the ionic compound?​

Answer 1

Answer:

In the unit cell, there are 8 corners.  

Cation A is present in alternative corners, i.e., 4 cations are present in the unit cell

However, every corner of the cell contributes ⅛ cations to the formula

Thus, the number of cation A contributed by the unit cell was = 4 x ⅛ = 0.5

The number of anion B  present on the diagonal = 1

Thus the unit cell contributes 1 Anion B to the formula

based on the above calculations, the ratio of cations to the anions in the formula was seen to be 0.5 : 1

After converting the ratio into whole numbers, the formula of the compound was seen to AB2.