Lewis Structures of Sulfur Trioxide (SO3) & Electrostatic Potentials (ESP)

Lewis Electron Dot Structure of Sulfur Trioxide SO₃ & Electrostatic Potentials ESP

A simple procedure for writing Lewis Structures was given in a previous article entitled “Lewis Structures and the Octet Rule”. Several worked examples relevant to this procedure were given in previous posts please see the Sitemap - Table of Contents (Lewis Electron Dot Structures).

The Lewis Electron Dot Structures of SO₃ were drawn using this procedure in a previous article entitled "Simple Procedure for writing Lewis Structures – Lewis Structures for sulfur trioxide SO₃"

Lewis structures #1 - #4 are the derived resonance structures:

 

Molecular Orbital Theory and ab initio calculations can be used to calculate and draw the electrostatic potential (ESP) of a molecule.

The molecular electrostatic potential is the potential energy of a proton at a particular location near a molecule. There are negative and positive ESP's.

Negative electrostatic potential corresponds to a attraction of the proton by the concentrated electron density in the molecules (mainly from lone pairs, pi-bonds,... ) (colored red). Red color in electrostatic potential drawings show areas with high electron density.

Positive electrostatic potential corresponds to repulsion of the proton by the atomic nuclei in regions where low electron density exists and the nuclear charge is incompletely shielded (colored blue). Blue color in electrostatic potential drawings show areas with low electron density.

Several ab initio softwares calculate electrostatic potentials based on quantum mechanically derived molecular orbitals. The electrostatic potential of SO₃ derived by ab initio calculations is shown below:

It is to be noted that most of the negative charge (electron rich areas, colored red) is concentrated on the oxygen atoms of SO₃ as it is expected from the Lewis structures of SO₃ and by chemical intuition. Most of the positive charge (electron deficient areas, colored blue) is concentrated on the S atom as it is expected from the Lewis structures of SO₃ and by chemical intuition.

 

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Relevant Posts

Lewis Structures|Octet Rule: A Simple Method to write Lewis Structures

Lewis structure of SO₂ – Simple Procedure for drawing Dot structures

Lewis Dot Structure of the sulfite ion SO₃-2

 

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References

1. G.N. Lewis, J.A.C.S, 38, 762-785, (1916)
2.  E. C. McGoran, J. Chem. Educ., 68, 19-23 (1991)
3. A.B.P. Lever, J. Chem. Educ., 49, 819-821, (1972)

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Key Terms

resonance structures of sulfur trioxide SO3, Lewis electron structures of SO3, chemical formula of SO3, simple method for drawing Lewis structures of SO3, electrostatic potential, ab initio,molecular orbital theory

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