How to draw SO3 Lewis Structure? - Science Education and Tutorials

The sulfur trioxide chemical formula is SO3. Drawing SO3 Lewis Structure is very easy to by using the following method. Here in this post, we described step by step method to construct SO3 Lewis Structure. The sulfur and oxygen elements come as the member of the oxygen family group from the periodic table. The valence electrons in sulfur and oxygen are six. The branch of sulfur chemistry is used to make chemicals reagents for sulfonation reactions.

Table of Contents

Key Points To Consider When Drawing The SO3 Electron Dot Structure

A three-step approach for drawing the SO3 Lewis structure can be used. The first step is to sketch the Lewis structure of the SO3 molecule, to add valence electrons around the sulfur atom; the second step is to add valence electrons to the three oxygen atoms, and the final step is to combine the step1 and step2 to get the SO3 Lewis Structure.

The SO3 Lewis structure is a diagram that illustrates the number of valence electrons and bond electron pairs in the SO3 molecule. The geometry of the SO3 molecule can then be predicted using the Valence Shell Electron Pair Repulsion Theory (VSEPR Theory), which states that molecules will choose the SO3 geometrical shape in which the electrons have from one another.

Finally, you must add their bond polarities to compute the strength of the three S-O double bonds (dipole moment properties of the SO3 molecule). The sulfur-oxygen bonds in sulfur trioxide(SO3), for example, are polarised toward the more electronegative oxygen in SO3 molecule, and because both bonds have the same size and located around three oxygen terminals of the trigonal planar with no lone pair (in total zero electrons) on the sulfur atom, their sum of dipole moment is zero due to the SO3 molecule’s bond dipole moment and more electron polarity to the oxygen atoms. Because each three S-O bonds polarity canceled each other in the SO3 molecule. The sulfur trioxide(SO3) molecule is classified as a nonpolar molecule.

The molecule of sulfur trioxide (with trigonal planar molecular geometry) is tilted, the bond angles between sulfur and oxygen are 120 degrees. It has a difference in electronegativity values between sulfur and oxygen atoms, with central sulfur’s pull being less than terminal oxygen’s in the SO3 molecule. But they canceled each other due to the symmetrical planar molecular geometry of the SO3 molecule.

As a result, it has the zero dipole moment. The SO3 molecule has a zero dipole moment due to an equal charge distribution of negative and positive charges. But both these atoms fall on the oxygen family group in the family. The oxygen atom is a more electronegative value than sulfur in the SO3 molecule. The SO3 molecule has the net dipole moment of zero value in the ground state energy level.

SO3 molecule has three S-O double bonds. It shows a shorter distance than the single bond. If it absorbs light may be from visible or UV light. It undergoes pi to pi star and n to pi star transition from ground state energy level to excited state energy level. In the excited state energy level, the SO3 molecule shows a definite dipole moment. But it is very dynamics.

Molecules can be classified as polar or nonpolar. The molecule polar behaves in a different manner as compared to nonpolar.

Overview: SO3 Lewis Structure

The central atom is sulfur, which is bordered on three terminals with oxygen atoms( in trigonal planar), and zero lone pair on the central in the trigonal planar geometry. Sulfur has six outermost valence electrons, indicating that it possesses six electrons in its outermost shell, whereas oxygen also has six valence electrons in its outermost shell. To complete the octet of the sulfur and oxygen atoms requires two valence electrons on each of their outermost shell.

Three oxygen atoms establish covalent connections with the central sulfur atom as a result, leaving the sulfur atom with zero lone pair. There are zero lone pair of electron on the sulfur central atom that resists the bond pairs of the three S-O bonds. According to VSEPR theory, the double S-O bond pairs polarity lead the SO3 molecule to take on the trigonal planar geometry structure.

The SO3 molecule’s three S-O bonds are arranged in symmetrical polarity order around the trigonal planar molecular geometry, giving rise to the SO3 molecular shape. The SO3 molecule has a trigonal planar molecular geometry because there is electrical repulsion between the lone pairs of electrons in oxygen and three double bond pairs(S-O) of the SO3 molecule.

Lewis structure of SO3 has dot electron representative structure. Valence electrons of atoms undergo orbitals mixing in the chemical reactions, gives new types of molecular species of SO3. The molecule is nothing but a bundle of valence electrons from the atoms. But it is converted to bond pairs and lone pairs in the molecular structure.

Electronegative value Difference Calculation of SO3 Molecule:

Sulfur and Oxygen Electronegative difference in SO3:

The sulfur atom has an electronegativity of 2.58, while oxygen has an electronegativity of 3.44 in the SO3 molecule. The difference in electronegativity of sulfur and oxygen can be estimated using the method below.

The electronegative value difference between sulfur and oxygen in SO3 molecule
Electronegativity value of sulfur = 2.58
Electronegativity value of oxygen= 3.44
Difference of electronegativity value between sulfur and oxygen in SO3 molecule = 3.44 – 2.58 = 0.86
Electronegativity difference between S-O bond calculation of SO3 molecule

The electronegative difference between sulfur and oxygen is greater than 0.5. This indicated the bond polarity moves near to polar nature. S-O bond polarity in the SO3 molecule is polar.

Because of this difference in electronegativity of sulfur and oxygen atoms, the SO3 molecule’s S-O bond becomes polar. The total net dipole moment of the SO3 molecule is zero due to the cancellation of the bond dipole moment in the trigonal planar geometry. The electronegativity of an atom is the strength with which it may attract bound electron pairs to its side. The polarity of SO3 is discussed in our previous post.

As a result, the S-O bond’s dipole moment is high due to the polarization of the bonds and zero lone pair of electrons on sulfur, and all S-O bonds’ dipoles are arranged in the symmetrical SO3 molecular geometry. The SO3 molecule has a zero net dipole moment.

The electron dot structure of the SO3 molecule is also known as the SO3 Lewis structure. It determines the number of outermost valence electrons as well as the electrons engaged in the SO3 molecule’s bond formation. The outermost valence electrons of the SO3 molecule must be understood while considering the Lewis structure of the molecule.

The sulfur atom is the middle element in SO3 molecular geometry, with six electrons in its outermost valence electron shell, whereas the oxygen atom has six electrons in its outermost valence electron shell. The oxygen atom has six valence electrons.

The SO3 has a total of 24 valence electrons as a result of the foregoing above-said reasoning. With the core central sulfur atom, the three terminals with three oxygen atoms form covalent bonds, leaving the sulfur atom with one lone pair in the middle of trigonal planar geometry.

Because lone pair on the terminal oxygen atoms create interaction with S-O bond pairs(but it is negligible in the ground state of the SO3 molecule). The bond angle of the O-S-O bond in the trigonal planar molecular geometry is approximately 120 degrees. This angle is greater than the CH4 molecule bond angle. The S-O bond length is 142pm(picometer).

To sketch the SO3 Lewis structure by following these instructions:

Step-1: SO3 Lewis dot Structure by counting valence electrons on the sulfur atom

To calculate the valence electron of each atom in SO3, look for its periodic group from the periodic table. The oxygen group families, which are the 16th group in the periodic table, are both made up of sulfur and oxygen atoms. In their outermost shells, oxygen and sulfur have six valence electrons.

Calculate the total number of valence electrons in the SO3 molecule’s outermost valence shell. The first step is to determine how many electrons are in the SO3 Lewis structure’s outermost valence shell. An electron in an atom’s outermost shell is known as a valence electron. It is represented by dots in the SO3 Lewis diagram. The SO3 molecule’s core sulfur atom can be represented as follows:

Total outermost valence shell electron of sulfur atom in SO3= 6
Total outermost valence shell electron of oxygen atom in SO3= 6
The SO3 molecule has one central sulfur and three oxygen atoms. Then the total outermost valence shell electrons can be calculated as follows
∴ Total outermost valence shell electrons available for SO3 Lewis structure( dot structure) = 6+3*6= 24 valence electrons in SO3.
calculation of total valence electron of SO3 molecule

Choose the atom with the least electronegative value atom and insert it in the center of the molecular geometry of SO3. We’ll choose the least electronegative value atom in the SO3 molecule to place in the center of the SO3 Lewis structure diagram in this phase. The electronegativity value in periodic groups grows from left to right in the periodic table and drops from top to bottom.

The first step is to put six valence electrons around the sulfur atom as given in the figure.

Step-2: Lewis Structure of SO3 for counting valence electrons around the terminal oxygen atoms

As a result, sulfur is the first atom in the periodic table’s oxygen family group. Oxygen is the first member of the oxygen family. The electronegative value of the oxygen atom is higher than that of the sulfur atom in the SO3 molecule. Furthermore, oxygen has a six electrons limit since sulfur is the less electronegative element in the SO3 molecule.

In the SO3 Lewis structure diagram, the sulfur atom can be the center atom of the molecule. As a result, central sulfur in the SO3 Lewis structure, with all three oxygen atoms arranged in trigonal planar geometry.

Add valence electrons around the oxygen atom, as given in the figure.

Step-3: Lewis dot Structure for SO3 generated from step-1 and step-2

Connect the exterior and core central atom of the SO3 molecule with three double S-O bonds. In this stage, use three oxygen atoms on the outside of the SO3 molecule to the central sulfur atom in the middle.

Count how many electrons from the outermost valence shell have been used in the SO3 structure so far. Each S-O double bond carries four electrons because each sulfur atom is connected to three oxygen atoms by three S-O double bonds. Bond pairings of S-O are what they’re called.

So, out of the total of 24 valence electrons available for the SO3 Lewis structure, we used 12 electrons for the SO3 molecule’s three S-O double bonds. The SO3 molecule has zero lone pair of electrons in the central sulfur atom.

Place the valence electrons in the S-O bond pairs starting with the core sulfur, three oxygen atoms in the SO3 molecule. In the SO3 Lewis structure diagram, we always begin by introducing valence electrons from the central sulfur atom(in step1). As a result, wrap around the central sulfur atom’s bond pair valence electrons first (see figure for step1).

The sulfur atom in the molecule gets only 12 electrons around its molecular structure. This central sulfur atom is extra octet stable. But it has zero lone pair. Sulfur compound(S8) is a yellowish solid in nature. when sulfur undergoes sublimation from solid state to gaseous state. But Sulfur is a very old anti-biotic for external uses.

Sulfur requires 12 electrons in its outermost valence shell to complete the molecular extra octet stability, 12 electrons bond pairs in three S-O double bonds. Then lone pairs of electrons on the oxygen atoms of the SO3 molecule are placed in a trigonal planar geometry. Sulfur already shares 12 electrons to the three S-O double bonds. Then place the valence electron in the oxygen atoms, it placed around six electrons on each atom(step-2). 12 valence electrons placed around three oxygen atoms as lone pairs of electrons.

We’ve positioned 12 electrons around the three terminal oxygen atoms(step-3), which is represented by a dot, in the SO3 molecular structure above. The sulfur atom completes its molecular extra octet stability in the SO3 molecule because it possesses 12 electrons in its (three S-O double bonds) bond pairs with three oxygen in the outermost valence shell.

Count how many outermost valence shell electrons have been used so far using the SO3 Lewis structure. three electron bond pairs are shown as dots in the SO3 chemical structure, whereas three double bonds each contain four electrons. The outermost valence shell electrons of the SO3 molecule(bond pairs) are 12 as a result of the calculation.

So far, we’ve used 24 of the SO3 Lewis structure’s total 24 outermost valence shell electrons. Zero lone pair of electrons on the sulfur atom in the trigonal planar of the SO3 molecule.

Complete the middle sulfur atom stability and, if necessary, apply a covalent bond. The central sulfur atom undergoes extra octet stability(due to three double bond pairs of electrons).

The core atom in the SO3 Lewis structure is sulfur, which is bonded to the three oxygen atoms by double bonds (three S-O). With the help of three double bonds, it already shares 12 electrons. As a result, the sulfur follows the extra octet rule and has 12 electrons surrounding it on the three terminals of the SO3 molecule’s trigonal planar geometry.

How to calculate the formal charge on sulfur and oxygen atoms in SO3 Lewis Structure?

Calculating formal charge on the sulfur of SO3 molecule:

The formal charge on the SO3 molecule’s sulfur central atom often corresponds to the actual charge on that sulfur central atom. In the following computation, the formal charge will be calculated on the central sulfur atom of the SO3 Lewis dot structure.

To calculate the formal charge on the central sulfur atom of the SO3 molecule by using the following formula:
The formal charge on the sulfur atom of SO3 molecule= (V. E(S)– L.E(S) – 1/2(B.E))
V.E (S) = Valence electron in a sulfur atom of SO3 molecule
L.E(S) = Lone pairs of an electron in the sulfur atom of the SO3 molecule.
B.E = Bond pair electron in S atom of SO3 molecule
calculation of formal charge on sulfur atom in SO3 molecule

The sulfur core atom (three double bonds connected to three oxygen atoms ) of the SO3 molecule has six valence electrons, zero lone pair of electrons(no electrons), and 12 bonding pairing valence electrons. Put these values for the sulfur atom in the formula above.

Formal charge on sulfur atom of SO3 molecule = (6- 0-(12/2)) =0

In the Lewis structure of SO3, the formal charge on the central sulfur atom is zero.

Calculating formal charge on the oxygen atom of SO3 molecule:

The formal charge on the SO3 molecule’s oxygen terminal atoms often corresponds to the actual charge on that oxygen terminal atoms. In the following computation, the formal charge will be calculated on the terminal oxygen atom of the SO3 Lewis dot structure.

To calculate the formal charge on the terminal oxygen atom of the SO3 molecule by using the following formula:
The formal charge on the oxygen atom of SO3 molecule= (V. E(O)– L.E(O) – 1/2(B.E))
V.E (O) = Valence electron in a oxygen atom of SO3 molecule
L.E(O) = Lone pairs of an electron in the oxygen atom of the SO3 molecule.
B.E = Bond pair electron in O atom of SO3 molecule
calculation of formal charge on oxygen atom in SO3 molecule

The oxygen terminal atoms of the SO3 molecule have six valence electrons, two lone pairs of electrons(four electrons), and four bonding pairing valence electrons(double bond). Put these values for the oxygen atom in the formula above.

Formal charge on oxygen atom of SO3 molecule = (6- 4-(4/2)) =0

In the Lewis structure of SO3, the formal charge on the terminal oxygen atom is zero.

Summary:

In this post, we discussed the method to construct the SO3 Lewis structure. First, the valence electrons are placed around the sulfur atom. Second, place the valence electron on the oxygen atoms. Finally, when we combined the first and second steps. It gives SO3 Lewis structure. Need to remember that, if you follow the above-said method, you can construct molecular dot structure very easily.