## Chemistry: The Molecular Science (5th Edition)

The only one that is not an exception is $SeF_2$. Meanwhile, in both $SF_6$ and $ClO_2$, the central atom, which in these cases is S and Cl, respectively, has too many valence electrons. Finally, $NH_4NO_3$ is an exception because it is ionically bonded and thus does not have a lewis dot structure.