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This is the electrostatic potential for ozone.

Electrostatic potential map of ozone

This is the electrostatic potential for sulfur dioxide.

SO2
(Click to enlarge)

They look almost exactly the same except one is all oxygen atoms and the other has sulfur in the center instead of oxygen.

Why does ozone have an MEP (molecular electrostatic potential) similar to that of SO2?

hBy2Py
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Caters
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  • Because their outer orbitals are very similar. The bonding nature in these to molecules is exactly the same with slightly more electronic structure moved from central atom in $\ce{SO2}$. – permeakra Aug 09 '14 at 20:27
  • yeah but 1 is polar(the sulfur dioxide) and the other is nonpolar with a positive charge(the ozone). I would expect that the positive charge of ozone would make the central oxygen pull harder in the bond(because of the positive charge it has) and thus the electrons spend less time around the terminal oxygens thus making the MEP more like the one of H2O – Caters Aug 09 '14 at 20:40
  • Ozone is non-polar? You might want to rethink that. – Dissenter Aug 09 '14 at 20:50
  • there is 0 dipole moment because all atoms in ozone have the same electronegativity. 0 dipole moment means nonpolar. However it is an ion to some degree because of the positively charged oxygen in the center. – Caters Aug 09 '14 at 20:56
  • charged molecule does not automatically mean polar. All it means is that it is an ion. You also have to take into consideration dipole moment(and thus electronegativity) to know whether it is a nonpolar ion(such as in the case of ozone), a polar ion(such as methoxide), or will participate in an ionic bond with another ion(as long as you know what that other ion is and its electronegativity). – Caters Aug 09 '14 at 21:07
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    @caters Ozone has dipole moment of ~ 0.5 D. It is three times smaller than for sulfur dioxide, but still high enough. And I repeat, both have roughly same electron structure. – permeakra Aug 09 '14 at 21:22
  • but the 3 Os all have the same electronegativity and isn't it electronegativity difference that determines dipole moment and thus polarity regardless of whether it is charged or not? – Caters Aug 09 '14 at 21:25
  • @caters Nope. Dipole moment is completely attributed to electron distribution in the molecule, and electron donation may go against electronegativity to some extent. – permeakra Aug 09 '14 at 21:35
  • @caters in fact dipole moment is a function of charge distribution. Electronegativity considerations allow to some extent predict some aspects of charge distribution in case of simple compounds with ordinary bonds. However, in case of molecules with dative bonds ($\ce{CO}$, $\ce{O3}$, $\ce{SO2}$ and many more), conjugated $\pi$-systems and other compounds with nontrivial electronic structures electronegativity alone does not work. – permeakra Aug 09 '14 at 21:54
  • Let us continue this discussion in chat. – Caters Aug 09 '14 at 23:02
  • @permeakra Sounds like you could write that up into a good answer! :) – tschoppi Oct 10 '14 at 16:40

1 Answers1

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Resonance structures of $\ce{SO2}$ and $\ce{O3}$.

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As you can see from the diagram $\ce{O3}$ and $\ce{SO2}$ are isoelectric and have the same shape and this accounts for their very similar electrostatic potential maps. Both molecules are polar although $\ce{SO2}$, with a dipole moment of 1.62D, is more polar than $\ce{O3}$ (0.53D). As the diagram shows, the polarity of both molecules is due to the their trigonal planar shape with a formal positive charge on the central atom.

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