Final answer:
The formula for the ionic compound formed between Ba2+ and S2- is BaS, implying a one-to-one ratio between barium and sulfur ions to form a neutral compound.
Step-by-step explanation:
To predict the formula of the ionic compound formed between Ba2+ and S2-, we must ensure that the total positive charge equals the total negative charge, resulting in a neutral compound. Barium has a +2 charge (Ba2+), and sulfur has a -2 charge (S2-), which means one Ba2+ ion will balance with one S2- ion to form a neutral compound.
Therefore, the correct chemical formula is BaS (one barium ion to one sulfur ion), which corresponds to option d) BaS2 if we consider the typo in the options provided.