The compound BaSO3 is known as barium sulfite.
Barium sulfite is formed from barium, a soft alkaline earth metal, and sulfite, which is the anion derived from sulfurous acid (H2SO3). In this compound, barium has a +2 oxidation state, while the sulfite ion carries a -2 charge. The formula represents one barium ion bonded to one sulfite ion.
Barium sulfite appears as a white solid and is often encountered in various industrial applications, particularly in the production of pigments and as a fireproofing agent.