How do I find the formula of Copper(1) Sulfide?

Question

Please explain in detail the steps in order to solve this equation.

Answer 1

The (I) in parentheses tells you the oxidation state of the copper.  This is known as the Stock method of nomenclature.  This tells you that the Cu is 1+ (as opposed to 2+ which would be Cu(II)).  Sulfide means it is the salt of the sulfur anion, which has a 2- oxidation number.  You can tell this from the periodic table where S is in group 6, meaning -2 state.

Thus, since Cu is 1+ and S is 2-, you will need two coppers for each sulfur.  The resulting formula is Cu₂S.