### VSEPR Structures of Odd Electron Molecules

Back to VSEPR Menu

All the usual rules of building a VSEPR structure will apply - minimize formal charge, build octect on more electronegative ligand first, etc.

**Example #1:** nitrogen dioxide NO_{2}

This molecule has a total of 17 electrons to place - five from the nitrogen and 12 from the oxygens. I will go immediately to the final structure:

Notice that I show both resonance structures.
Since there are three electron domains, this is a trigonal planar arrangement, but it is signified AX_{2}e, to signal the single electron domain, also called a half-filled orbital.

The bond angles are not 120°, since the repulsive power of the single electron is less tha if there were two. So, the O-N-O bond angle moves outward to 134.3°. Adding another electron to make NO_{2}¯ (which creates a full non-bonding electron pair, changes the O-N-O angle to 115.4° and removing an electron (to make NO_{2}^{+}) creates an O-N-O bond angle of 180°.

**Example #2:** chlorine dioxide ClO_{2}

The substance has 19 electrons to place and is a tetrahedral family member. Its geometry can be described as AX_{2}Ee. It will have a non-bonding pair and a non-bonding single electron.

Your assignment is to draw this structure. One hint: if you draw it singly bonding, you will arrive at a structure with a formal charge of +2 on the Cl and -1 on each oxygen. Draw a structure to remove those; the correct structure having no formal charge separation whatsoever.

The O-Cl-O bond angle in ClO_{2} is 118°. You may wish to ponder the effect on the bond angle in ClO_{2}^{+} and ClO_{2}¯.

Back to VSEPR Menu