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.

 

---

 

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

 

---

 

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)

---

 

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

u>

 

---

Lewis Structures & the Octet Rule - Theory & Examples

LEWIS STRUCTURES AND THE OCTET RULE - THEORY & EXAMPLES

SO2, SO3, SO3-2, SO4-2	Lewis Structures & the Octet Rule	H2CO3, CO, CO2, CO3-2
SCN-, OCN-, NCN-2	HCN, CN+, CN-, O3	COCl2, CS2, HNCHNH2
NO, NO2, NO2+, NO2-	NO3-, HNO3, NOCl	N2O, N2O3, N2O4, N2O2
N2F+, CF3NO, HO2NO2	HClO3, HClO4, Cl2O4	ClO2, ClO2+
Cr2O7-2 , CrO4-2 , CrO3, H2CrO4	PO4-3, PO3-, HO4P-2	P2H2, POCl3, IO3-
CH2N2, CN2H2, N2H3+, N3-	SO2Cl, HSO3Cl, S2O6	C2O4-2, BrO3-, N5+
CH3NO2, CH2NH, C2-2	CH3COOCH3, CH3CONH2, C3H4	C3H5+, C3H3N, BF
Lewis Structures	Lewis Structures	Lewis Structures
Lewis Structures	Lewis Structures	Lewis Structures

 

Lewis structures constitute an overwhelming majority of the structures that students encounter in courses in general chemistry, organic chemistry, or biochemistry. Hence, the writing of Lewis structures corresponding to a given molecular formula is an important exercise for them. The ability of students to write these structures correctly and then to calculate the formal charges of the atoms involved, is a prerequisite to understanding such topics as:

Resonance
Reactivity
Acidity and basicity
Bond and molecular polarities
Inter- and intra-molecular bonding
Isomerism and molecular geometry.

Since many chemistry textbooks do not give easy procedures for writing such structures an easy four-step method is presented and several worked-examples are given(1-3).

 

---

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)

---

Help with Lewis electron dot structures | Chlorine Perchlorate Cl2O4

Simple Method for writing Lewis Electron Dot Structures

of chlorine perchlorate Cl₂O₄

A simple procedure for writing Lewis electron dot structures is 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).

Another example  for writing Lewis structures following the above procedure is given below.

Let us consider the case of the Lewis electron dot structures of chlorine perchlorate Cl₂O₄

How can we construct the Lewis structure of Cl₂O₄?

 

Step 1: Connect the atoms with single bonds.

 

Step 2: Calculate the # of electrons in π bonds (multiple bonds) using  formula (1) in the article entitled “Lewis Structures and the Octet Rule”. 

Where n in this case is 6 since Cl₂O₄ consists of six atoms.

Where V = (6 + 7 + 6 * 2 + 6 + 7) = 38   

Therefore, P = 6n + 2 – V = 6 * 6 + 2 – 38 = 0

So there are no π electrons in Cl₂O₄ and therefore the structure of Step 1 is the Lewis structure.

Electrons are placed around each atom so that the octet rule is obeyed. Formal charges are assigned and equalized using resonance.

 

Step 3 & 4: The Lewis structures for Cl₂O₄ are derived below:

Electron Dot Structures of peroxy nitric acid HO₂NO₂

A simple procedure for writing electron dot structures (Lewis structures) is 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).

Another example  for writing Lewis structures following the above procedure is given below.

Let us consider the case of of peroxy nitic acid (HO₂NO₂) (known also as PAN HNO₄).

Peroxynitric acid HNO₄ plays an important role in the coupling of atmospheric HOx and NOx cycles⁴, especially at low temperatures. PNA serves as an important HOx and NOx reservoir species altering the oxidative capacity of the atmosphere on regional and global scales⁵. PNA is formed via the reaction of HO₂ and NO₂.

Let us draw the HO₂NO₂ electron dot structures?

 

Step 1: Connect the atoms with single bonds.

The central atom will be the N atom since it is the less electronegative (H is a terminal atom – it cannot be a central atom).

 

Step 2:

Calculate the # of electrons in π bonds (multiple bonds) using  formula (1) in the article entitled “Lewis Structures and the Octet Rule”. 

Where n in this case is 5 since HO₂NO₂ consists of six atoms but one of them is a H atom.

Where V = (1 + 6 + 6 + 5 + 6 + 6) = 30

Therefore, there are 2 π electrons in HO₂NO₂ and so 1 double bond must be added to the structure of Step 1.

 

Step 3 & 4: One double bond must therefore be placed through the 3 N-O bonds. Therefore, the Lewis electron dot structures for HO₂NO₂ are as follows:

Stuctures #1 and #2 are the more plausible (more stable) due to smaller charge separation.

---

 

Relevant Posts - Relevant Videos

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

Simple Method for writing Lewis Structures – Lewis Structures of CF₃NO

 

---

 

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)
4. H. Niki et al., Chem. Phys. Lett., 45, 564-566 (1977)
5. S. Kim et al., J. Geophys. Res.-Atmos., 112, D12S01 (2007)

---

 

Key Terms

resonance structures of HO2NO2 peroxy nitric acid , Lewis electron structures of , chemical formula of HO2NO2 peroxy nitric acid, simple procedure for drawing Lewis structures of PNA peroxy nitric acid,

 

---

Lewis dot of Nitrogen Monoxide (NO)

A simple procedure for writing Lewis Structures is 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 index page Lewis Structures & the Octet Rule - Theory & Examples.

Another example for writing Lewis structures following the above procedure is given in this post. The Lewis structures of Nitrogen Monoxide NO are drawn.

Let us consider the case of NO. NO is a free radical and is an important intermediate in the chemical industry. Nitric oxide is a by-product of combustion of substances as in automobile engines, fossil fuel power plants, and is produced naturally during the electrical discharges of lightning in thunderstorms. In mammals including humans, NO is an important cellular signaling molecule involved in many physiological and pathological processes. The vasodilating antihypertensive drug minoxidil contains an NO moiety and may act as an NO agonist. Likewise, Sildenafil citrate, popularly known by the trade name Viagra, stimulates erections primarily by enhancing signaling through the nitric oxide pathway in the penis.

Let us draw the Lewis dot structures of Nitrogen Monoxide (NO).

Step 1:   Connect the N with the O atom with single bonds

Step 2: Calculate the # of electrons in π bonds (pi bonds, multiple bonds) using formula (1) in the article entitled “Lewis Structures and the Octet Rule”. 

Where n in this case is 2 since NO consists of two atoms.

Where V = 5 +6  = 11 , V is the number of valence electrons of the ion.

Therefore, P = 6n + 2 – V = 6 * 2 + 2 – 11  = 3     So, there is 1 double bond and an electron.

Step 3 & 4: The  Lewis dot resonance structures of Nitrogen Monoxide (NO) are as follows:

---

Relevant Posts - Relevant Videos

Lewis Structures and the Octet Rule

Simple Procedure for writing Lewis Structures – Lewis Structures for NO2+ and HCN

Simple Procedure for writing Lewis Structures – Lewis Structures for nitrogen dioxide (NO2)

---

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)

---

Key Terms

lewis structures of nitrogen monoxide NO, simple method for writing Lewis structures, valence electrons, single bonds, electrons in π bonds, resonance structures, electron dot structures of nitrogen monoxide NO