Barium ions are extremely toxic to most living things, especially humans. And yet, despite its toxicity, barium sulfate cocktails are often given to patients undergoing a CAT scan because barium readily absorbs X-rays and can therefore serve as a contrast medium which helps in the imaging of internal organs. Based on what you learned in this chapter, suggest a reason why barium sulfate may be safe to ingest despite the extreme toxicity of the Ba²⁺ ion. What do you think will be the fate of the person who is given a barium carbonate cocktail instead?