Final answer:
The charge on the ion formed by element G in the compound GS2 must be 4+ to balance the 4- charge from the two sulfide ions, resulting in a neutral ionic compound.
Step-by-step explanation:
If an element G reacts with sulfur to form an ionic compound with the chemical formula GS2, the sulfide ion (S²-) has a charge of 2-. Therefore, to balance the charges in the ionic compound GS2, the element G must provide a total positive charge that equals the combined negative charge of the two sulfide ions. Since each sulfide ion has a charge of 2-, the total negative charge is 4-, and so the charge on the ion formed by G must be 4+ in order to balance the two 2- charges from the sulfide ions, thus giving a neutral compound.