Question #5f272

1 Answer
Mar 17, 2015

Nitrogen dioxide, or #NO_2#, is an odd-electron molecule, i.e. the number of valence electrons the molecule has is not an even number.

More specifically, nitrogen dioxide has a total of 17 valence electrons - 5 from nitrogen and 6 from each of the two oxygen atoms that comprise the molecule.

Now, VSEPR Theory can be extended to accomodate odd-electron molecules. In this case, the nitrogen dioxide molecule is considered to have a #AX_2E_0.5# geometry, which is right between #AX_2E_0# - linear, and #AX_2E_1# - bent.

The molecule's geometry will still be closer to bent, but the bond angle will be larger than the ideal #120^@# such a geometry predicts, mostly because the oxygen atoms experience less repulsion from the single electron present on the nitrogen atom.

The actual bond angle for nitrogen dioxide is #134^@#. By comparison, the angle found in the nitrite ion, or #NO_2^(-)#, is #115.4^@#, because now nitrogen has attached a full lone pair of electrons that experience greater repulsion with the oxygen atoms.