1. The formula is LiF (lithium fluoride). The cation is Li (and there is one) and the anion is F (there is one too), so the ratio between cation-anion is 1:1.
2. The formula is Na2O (sodium oxide). The cation (metal) is Na and there are two atoms. And the anion (nonmetal) is oxygen and there is one. The cation-anion ratio is 2:1.
3. The formula is AlPO4 (aluminum phosphate), where cation is Al and PO4 is the anion. The ratio between cation and anion is 1:1.
4. The formula is AlF3 (aluminum fluoride), where cation is Al (there is one atom) and the anion is F (there are three atoms of F), so the cation-anion ratio is 1:3.
5. The formula is Fe2S3 (iron sulfate). The cation is Fe (we have two atoms of Fe) and the anion is S (we have three atoms of S), so the cation-anion ratio is 2:3.