how do you find the formula for aluminium sulfide?

Question

i get Al-5 S-2 but from here i cannot get it to Al2 S3, btw i have not been taught how to find the chemical formula for certain substances so if you could also tell me the steps on how to do it, it would be great and greatly acknowledged

Answer 1

Al has a valence # of +3
S has a valence # of -2
2*(+3_+3*(-2)=0 for bakance, therefore
Al2S3

Answer 2

Take the oxidation state for the metal and the nonmetal...Al is metal, S is non metal... Divide the smaller number into the larger number, and that will tell you how many of the smaller oxidation states atoms you need per one larger. Ex. Fl has an oxidation state of -1 (wants one electron, has 7 valance electrons), and Rb has an oxidation state of +1 (has one valance electron and wants to get rid of it...happy eight rule...always wants eight valance electrons, or none) Since their an even devision you need one Fl for every one Rb, so it would RbFl (Rubiduium Fluide...spellings off?) Any good periodic table has the oxidation states, and MSDS's have them to, but their easy to find online.

Answer 3

Aluminum ions (Al3+) and sulfide ions (S2-) combine to give aluminum sulfide, Al2S3


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