# What is the chemical formula for sodium sulfite?

You should know what a sodium ion looks like: $N {a}^{+}$
A sulfate ion is $S {O}_{4}^{2 -}$, but we want -ite. This suffix generally means one less oxygen atom in that specific oxyanion. The sulfite ion is $S {O}_{3}^{\textcolor{w h i t e}{x} 2 -}$.
Ionic compounds are neutral; that is, they have a net charge of $0$. We need $2$ $N {a}^{+}$ ions to neutralize the charge of $S {O}_{3}^{\textcolor{w h i t e}{x} 2 -}$. So moving forward with this knowledge, the formula for the ionic compound is...
$N {a}_{2} S {O}_{3}$