I'm not sure if you're asking for more than one answer but S04 is one of them, you can search it up if you don't believe me
ion with the subscript of the atoms in a polyatomic ion. There is only ONE Cu and ONE S04, so get the charge for the Cu based on the S04. The formula is S04 , and there is only ONE S04 2, so Cu's charge here must be +2 for the compound to have an overall charge of zero. = copper (Il) ion S04 = sulfate ion then CuS04 = copper (Il) sulfate
