Write the formal charges on atoms in $CO_3^{2-}$ and $HNO_3$.

The formal charge on an atom in a Lewis structure is calculated as: $FC = [\text{Total number of valence electrons}] - [\text{Total number of non-bonding electrons}] - \frac{1}{2} [\text{Total number of bonding electrons}]$.
For $CO_3^{2-}$:
$1$. Carbon atom: $FC = 4 - 0 - \frac{1}{2}(8) = 0$.
$2$. Double-bonded Oxygen: $FC = 6 - 4 - \frac{1}{2}(4) = 0$.
$3$. Single-bonded Oxygen atoms (two): $FC = 6 - 6 - \frac{1}{2}(2) = -1$.
For $HNO_3$ (in the structure $H-O-N(=O)_2$):
$1$. Hydrogen: $FC = 1 - 0 - \frac{1}{2}(2) = 0$.
$2$. Hydroxyl Oxygen: $FC = 6 - 4 - \frac{1}{2}(4) = 0$.
$3$. Nitrogen: $FC = 5 - 0 - \frac{1}{2}(8) = 1$.
$4$. Double-bonded Oxygen: $FC = 6 - 4 - \frac{1}{2}(4) = 0$.
$5$. Single-bonded Oxygen (dative bond): $FC = 6 - 6 - \frac{1}{2}(2) = -1$.