Draw the resonance structures of $CO_2$.

The resonance structures of $CO_2$ involve the shifting of lone pairs and pi electrons between the carbon and oxygen atoms. The three contributing resonance structures are as follows:
$: \ddot{O}^{\ominus}-C \equiv O:^{+} \leftrightarrow :\ddot{O}=C=\ddot{O}: \leftrightarrow :^{+}O \equiv C-\ddot{O}^{\ominus}:$