Write the resonance structures for $SO_{3}$,$NO_{2}$,and $NO_{3}^{-}$.

(N/A) The resonance structures are as follows:
$1$. $SO_{3}$:
Total valence electrons $= 6 + 3(6) = 24$.
Resonance involves the delocalization of $\pi$ electrons among the three $S-O$ bonds.
$2$. $NO_{2}$:
Total valence electrons $= 5 + 2(6) = 17$.
This is an odd-electron molecule where the unpaired electron is delocalized between the two oxygen atoms.
$3$. $NO_{3}^{-}$:
Total valence electrons $= 5 + 3(6) + 1 = 24$.
The negative charge is delocalized over the three oxygen atoms,resulting in three equivalent resonance structures.