How do you balance the equation for FeS?

Since it is an ionic compound, the overall charge should be zero. Iron (Fe) has possible different charges which are +2, and +3 however sulfide always has a charge of -2. Therefore, FeS is already balanced. When you write it, instead of writing "Iron Sulfide", you would write "Iron (II) Sulfide" this is because Iron has different charges and you must specify when you write it down.