## Chemistry: The Central Science (13th Edition)

In order to fill this table, we have to balance charges on anions and cations. For example: $Na^{+}$ and $NO_{3}^ {-}$, The charges are balanced so the chemical formula will be $NaNO_{3}$ For $Ca^{+2}$ and $NO_{3}^ {-}$, We need two ions of $NO_{3}^ {-}$, thus the chemical formula will be $Ca(NO_{3})_{2}$ For $Fe^{2+}$ and $AsO_{4}^{3-}$, We need three ions of $Fe^{2+}$ ( $3×+2=+6$ ) and two ions of $AsO_{4}^{3-}$ ($2×−3=−6$ ). Thus the chemical formula will be $Fe_{3}(AsO_{4})_{2}$. The rest of the table is filled in this way.