You can't balance the equation "Fe + S --- Fe2" because it's not a complete or accurate chemical reaction. Here's why:

* Fe2 doesn't exist: Iron (Fe) doesn't form a diatomic molecule like oxygen (O2) or nitrogen (N2).

* Incomplete reaction: The equation is missing the product of the reaction between iron and sulfur.

The correct reaction:

The reaction between iron (Fe) and sulfur (S) produces iron sulfide (FeS):

Fe + S → FeS

Balancing the Equation:

This equation is already balanced as it stands.

* There's one iron atom (Fe) on each side of the equation.

* There's one sulfur atom (S) on each side of the equation.

Let me know if you'd like to balance any other chemical reactions!