What is the Formula of Barium Sulphate?

To build the formula, you must look at the valency (charge) of the two massive ions involved:

1. The Barium Cation: Barium (Ba) belongs to Group 2 of the periodic table, so it loses 2 electrons. Its charge is Ba²⁺.
2. The Sulphate Anion: Sulphate is a complex polyatomic ion made of sulfur and oxygen. Its strict permanent charge is SO₄²⁻.

Because the +2 positive charge of Barium perfectly cancels out the -2 negative charge of Sulphate, they lock together in a simple 1:1 ratio. Therefore, you do not write Ba₂(SO₄)₂; you simplify it to just BaSO₄.

In board exams, this chemical is incredibly famous because it is completely insoluble in water. When you mix clear Barium Chloride liquid with clear Sodium Sulphate liquid, a massive chemical reaction instantly occurs, and thick, milk-like solid flakes of BaSO₄ instantly crash out of the liquid and fall to the bottom of the test tube. This is called a White Precipitate. Reaction: BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s)↓ + 2NaCl(aq)

Because Barium Sulphate is a heavy, dense metal compound that cannot dissolve in the human stomach, doctors use it brilliantly in medicine. If a patient has a stomach ulcer, the doctor makes them drink a thick, chalky milkshake of pure BaSO₄. Because the heavy Barium blocks X-Ray lasers, the doctor can take a perfect, glowing X-ray photograph of the inside of the patient's stomach.