See the image below..?

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Answer 1 · 2016-09-24T17:40:30

The compound could be $"CaF"_2$ .

The big atoms ( $bb"B"$ ) are counted as:

The small atoms ( $bb"A"$ ) are counted as:

Total = 4 $"A"$ atoms.

The formula is $"B"_8"A"_4$ or $"AB"_2$ .

The formula must be either $"CaF"_2$ or $"SO"_2$ .

$"SO"_2$ is a covalent compound. It would exist as discrete molecules in the unit cell.

Hence, the compound must be $"CaF"_2$ (fluorite).

Here's a better picture of the fluorite unit cell, that makes it easier to count the atoms.