Here's why:
* Potassium (K) is a Group 1 element, meaning it forms a +1 ion (K⁺).
* Sulfide (S) is a Group 16 element, meaning it forms a -2 ion (S⁻²).
To balance the charges, you need two potassium ions (2 x +1 = +2) for every one sulfide ion (-2).
Therefore, the formula for potassium sulfide is K₂S. Since the subscript for potassium is 2, the subscript of potassium in the formula for sulfide is 1.
