What is the chemical formula for arsenite?

The chemical formula for arsenite is AsO3(3-). Arsenite refers specifically to the anion formed by arsenic that is in the +3 oxidation state and is associated with three oxygen atoms.

In the context of the options provided, the formula AsO3(3-) correctly indicates that there are three oxygen atoms bonded to arsenic, and the negative three charge reflects the overall charge of the arsenite ion. This makes it a distinct species compared to other choices that represent different anions.

For instance, AsO4(3-) represents arsenate, which contains four oxygen atoms and corresponds to arsenic in the +5 oxidation state. The other options, such as BO3(3-) and BrO3(-), refer to borate and bromate respectively, which are entirely different ions associated with boron and bromine, not arsenic. Understanding these distinctions confirms why AsO3(3-) is the correct chemical formula for arsenite.