The ratio of Al^3+ ions to S^2- ions in a neutral compound is 2:3.
The neutral compound formed by aluminum ion and sulphide ion is aluminium sulphide, with chemical formula Al2S3. Looking at the chemical equation, you will observe that, for each molecule of aluminium sulphide, there is two atoms of aluminium and three atoms of sulphur. This is the ratio of combination for the compound, that is, for every two atoms of aluminium, there are three atoms of sulphur, thus, the combination ratio is 2:3.
