SO3 Molecular Geometry

SO3 Molecular Geometry / Shape and Bond Angles (Sulfur Trioxide)
SO3 Molecular Geometry / Shape and Bond Angles (Sulfur Trioxide)

Sulfur trioxide(SO3) has the composition of one sulfur and three oxygen atoms. What is the molecular geometry of sulfur trioxide?. Drawing and predicting the SO3 molecular geometry is very easy by following the given method. Here in this post, we described step by step to construct SO3 molecular geometry. Sulfur and oxygen come from the 16th family group in the periodic table. Sulfur and oxygen have six valence electrons.

Key Points To Consider When drawing The SO3 Molecular Geometry

A three-step approach for drawing the SO3 molecular can be used. The first step is to sketch the molecular geometry of the SO3 molecule, to calculate the lone pairs of the electron in the central sulfur atom; the second step is to calculate the SO3 hybridization, and the third step is to give perfect notation for the SO3 molecular geometry.

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

Finally, you must add their bond polarities characteristics to compute the strength of the three S-O double bonds (dipole moment properties of the SO3 molecular geometry). Three sulfur-oxygen double bonds in the sulfur trioxide(SO3), for example, are polarised toward the more electronegative value oxygen atoms, and because all three (S-O) double bonds have the same size and polarity, their sum is zero due to the SO3 molecule’s bond dipole moment due to pulling the electron cloud to the three side of trigonal planar geometry, and the SO3 molecule is classified as a polar molecule.

The molecule of sulfur trioxide(with trigonal planar shape SO3 molecular geometry) is tilted at 120 degrees bond angle of O-S-O. It has a difference in electronegativity values between sulfur and oxygen atoms, with oxygen’s pull the electron cloud being greater than sulfur’s. But bond polarity of S-O is canceled to each other in the trigonal planar geometry. As a result, it has a zero permanent dipole moment in its molecular structure. The SO3 molecule has a zero dipole moment due to an equal charge distribution of negative and positive charges in the trigonal planar geometry.

Overview: SO3 electron and molecular geometry

According to the VSEPR theory, the SO3 molecule ion possesses trigonal planar molecular geometry. Because the center atom, sulfur, has three S-O double bonds with the three oxygen atoms surrounding it. The O-S-O bond angle is 120 degrees in the trigonal planar SO3 molecular geometry. The SO3 molecule has a trigonal planar geometry shape because it contains three oxygen atoms in the plan and all bonds are double bonded with resonance structure.

There are three S-O double bonds at the SO3 molecular geometry. After linking the three oxygen atoms and zero lone pair of electron on the sulfur atom in the trigonal planar form, it maintains the trigonal planar shaped structure. In the SO3 molecular geometry, the S-O double bonds have stayed in the three terminals and zero lone pair of electron on the sulfur atom of the trigonal planar molecule.

The center sulfur atom of SO3 has zero lone pair of electron, resulting in trigonal planar SO3 electron geometry. However, the molecular geometry of SO3 looks trigonal planar shaped and zero lone pair of electron on the sulfur of the SO3 geometry. It’s the SO3 molecule’s symmetrical geometry. As a result, the SO3 molecule is nonpolar.

How to find SO3 hybridization and molecular geometry

Calculating lone pairs of electrons on sulfur in the SO3 geometry:

1.Determine the number of lone pairs of electrons in the core sulfur atom of the SO3 Lewis structure. Because the lone pairs of electrons on the sulfur atom are mostly responsible for the SO3 molecule geometry planar, we need to calculate out how many there are on the central sulfur atom of the SO3 Lewis structure.

Use the formula below to find the lone pair on the sulfur atom of the SO3 molecule.

L.P(S) = V.E(S) – N.A(S-O)/2

Lone pair on the central sulfur atom in SO3 = L.P(S)

The core central sulfur atom’s valence electron in SO3 = V.E(S)

Number of S-O bonds = N.A (S-O)

calculation for sulfur atom lone pair in SO3 molecule.

For instance of SO3, the central atom, sulfur, has six electrons in its outermost valence shell, three S-O double bond connections. This gives a total of six connections.

As a result of this, L.P(S) = (6 –6)/2=0

The lone pair of electrons in the sulfur atom of the SO3 molecule is zero.

Calculating lone pair of electrons on oxygen in the SO3 geometry:

Finding lone pair of electrons for the terminal atom is not similar to the central sulfur atom. We use the following formula as given below

Use the formula below to find the lone pair on the oxygen atom of the SO3 molecule.

L.P(O) = V.E(O) – N.A(S-O)

Lone pair on the terminal oxygen atom in SO3 = L.P(O)

Terminal oxygen atom’s valence electron in SO3 = V.E(O)

Number of S-O bonds = N.A ( S-O)

calculation for oxygen atom lone pair in SO3 molecule.

For instance of SO3, their terminal atoms, oxygen, have six electrons in its outermost valence shell, one S-O double bond connection. This gives a total of three S-O double bond connections. But we are considering only one connection for the calculation.

As a result of this, L.P(O) = (6 –2)=4

The lone pair of electrons in the oxygen atom of the SO3 molecule is four. Three oxygen atoms are connected with the central sulfur atom.

In the SO3 electron geometry structure, the lone pair on the central sulfur atom is zero, lone pairs of electrons in the oxygen atom have four. Three oxygen atoms have 12 lone pairs of electrons.

It means there are one lone pair of electrons in the core sulfur atom. One lone pair of electrons on the central sulfur atom is responsible for the trigonal planar nature of SO3 molecular geometry. But in the structure oxygen atoms are polarised sidewise in their planar geometry.

The one lone pair of electrons are placed at another side of the SO3 geometry. Because the sulfur atom is a lower electronegative value as compared with other atoms in the SO3 molecule. Three oxygen atoms are polarized towards the sidewise in the SO3 structure.

But in reality, the SO3 has one lone pair of electrons in its structure. This makes the SO3 more symmetrical in the structure of the molecule. Because there is no electric repulsion between bond pairs and lone pairs. But some sort of interaction is there between oxygen lone pairs and bond pairs. But it is negligible in the ground state.

Calculate the number of molecular hybridizations of the SO3 molecule

What is SO3 hybridization? This is a very fundamental question in the field of molecular chemistry. All the molecules are made of atoms. In chemistry, atoms are the fundamental particles. There are four different types of orbitals in chemistry. They are named s, p, d, and f orbitals.

The entire periodic table arrangement is based on these orbital theories. Atoms in the periodic table are classified as follows:

s- block elements

p- block elements

d-block elements

f-block elements

Atoms are classified in the periodic table

SO3 molecule is made of one sulfur, three oxygen atoms. The oxygen and sulfur atoms have s and p orbitals. Oxygen comes as the first element from the oxygen family in the periodic table. The sulfur atom also belongs to the same family group. But it falls as the second element in the periodic table.

When these atoms combine to form the SO3 molecule, its atomic orbitals are mixed and form unique molecular orbitals due to hybridization.

How do you find the SO3 molecule’s hybridization? We must now determine the molecular hybridization number of SO3.

The formula of SO3 molecular hybridization is as follows:

No. Hyb of SO3= N.A(S-O bonds) + L.P(S)

No. Hy of SO3 = the number of hybridizations of SO3

Number of S-O bonds = N.A (S-O bonds)

Lone pair on the central sulfur atom = L.P(S)

Calculation for hybridization number for SO3 molecule

In the SO3 molecule, sulfur is a core central atom with three oxygen atoms connected to it. It has zero lone pair of electrons on sulfur. The number of SO3 hybridizations (No. Hyb of SO3) can then be estimated using the formula below.

No. Hyb of SO3= 3+0=3

The SO3 molecule ion hybridization is three. The sulfur and oxygen atoms have s and p orbitals. The sp2 hybridization of the SO3 molecule is formed when one s orbital and two p orbitals join together to form the SO3 molecular orbital.

Molecular Geometry Notation for SO3 Molecule :

Determine the form of SO3 molecular geometry using VSEPR theory. The AXN technique is commonly used when the VSEPR theory is used to calculate the shape of the SO3 molecule.

The AXN notation of SO3 molecule is as follows:

The central sulfur atom in the SO3 molecule is denoted by the letter A.

The bound pairs (three S-O bonds) of electrons to the core sulfur atom are represented by X.

The lone pairs of electrons on the central sulfur atom are denoted by the letter N.

Notation for SO3 molecular geometry

We know that SO3 is the core atom, with three electron pairs bound (three S-O) and zero lone pair of electrons. The general molecular geometry formula for SO3 is AX3.

According to the VSEPR theory, if the SO3 molecule ion has an AX3 generic formula, the molecular geometry and electron geometry will both trigonal planar forms.

Name of Molecule Sulfur trioxide
Chemical molecular formula SO3
Molecular geometry of SO3 Trigonal planar
Electron geometry of SO3 Trigonal planar
Hybridization of SO3 sp2
Bond angle (O-S-O) 120º degree
Total Valence electron for SO3 24
The formal charge of SO3 on sulfur 0


In this post, we discussed the method to construct SO3 molecular geometry, the method to find the lone pairs of electrons in the central sulfur atom, SO3 hybridization, and SO3 molecular notation. Need to remember that, if you follow the above-said method, you can construct the SO3 molecular structure very easily.

What is SO3 Molecular geometry?

SO3 Molecular geometry is an electronic structural representation of molecules.

What is the molecular notation for SO3 molecule?

SO3 molecular notation is AX3.

The polarity of the molecules

Polarity of the molecules are listed as follows

  • Polarity of BeCl2
  • Polarity of SF4
  • Polarity of CH2Cl2
  • Polarity of NH3
  • Polarity of XeF4
  • Polarity of BF3
  • Polarity of NH4+
  • Polarity of CHCl3
  • Polarity of BrF3
  • Polarity of BrF5
  • Polarity of SO3
  • Polarity of SCl2
  • Polarity of PCl3
  • Polarity of H2S
  • Polarity of NO2+
  • Polarity of HBr
  • Polarity of HCl
  • Polarity of CH3F
  • Polarity of SO2
  • Polarity of CH4

Lewis Structure and Molecular Geometry

Lewis structure and molecular geometry of molecules are listed below

  • CH4 Lewis structure and CH4 Molecular geometry
  • BeI2 Lewis Structure and BeI2 Molecular geometry
  • SF4 Lewis Structure and SF4 Molecular geometry
  • CH2I2 Lewis Structure and CH2I2 Molecular geometry
  • NH3 Lewis Structure and NH3 Molecular geometry
  • XeF4 Lewis Structure and XeF4 Molecular geometry
  • BF3 Lewis Structure and BF3 Molecular geometry
  • NH4+ Lewis Structure and NH4+ Molecular geometry
  • CHCl3 Lewis Structure and CHCl3 Molecular geometry
  • BrF3 Lewis Structure and BrF3 Molecular geometry
  • BrF5 Lewis Structure and BrF5 Molecular geometry
  • SO3 Lewis Structure and SO3 Molecular geometry
  • SI2 Lewis structure and SI2 Molecular Geometry
  • PCl3 Lewis structure and PCl3 Molecular Geometry
  • H2S Lewis structure and H2S Molecular Geometry
  • NO2+ Lewis structure and NO2+ Molecular Geometry
  • HBr Lewis structure and HBr Molecular Geometry
  • CS2 Lewis structure and CS2 Molecular Geometry
  • CH3F Lewis structure and CH3F Molecular Geometry
  • SO2 Lewis structure and SO2 Molecular Geometry
  • HCl Lewis structure and HCl Molecular Geometry
  • HF Lewis structure and HF Molecular Geometry
  • HI Lewis structure and HI Molecular Geometry
  • CO2 Lewis structure and CO2 Molecular Geometry
  • SF2 Lewis structure and SF2 Molecular Geometry
  • SBr2 Lewis structure and SBr2 Molecular Geometry
  • SCl2 Lewis structure and SCl2 Molecular Geometry
  • PF3 Lewis structure and PF3 Molecular Geometry
  • PBr3 Lewis structure and PBr3 Molecular Geometry
  • CH3Cl Lewis structure and CH3Cl Molecular Geometry
  • CH3Br Lewis structure and CH3Br Molecular Geometry
  • CH3I Lewis structure and CH3I Molecular Geometry
  • SCl4 Lewis structure and SCl4Molecular Geometry
  • SBr4 Lewis structure and SBr4 Molecular Geometry
  • CH2F2 Lewis structure and CH2F2 Molecular Geometry
  • CH2Br2 Lewis structure and CH2Br2 Molecular Geometry
  • XeCl4 Lewis structure and XeCl4 Molecular Geometry
  • BCl3 Lewis structure and BCl3 Molecular Geometry
  • BBr3 Lewis structure and BBr3 Molecular Geometry
  • CHF3 Lewis structure and CHF3 Molecular Geometry
  • CHBr3 Lewis structure and CHBr3 Molecular Geometry
  • ClF3 Lewis structure and ClF3 Molecular Geometry
  • IF3 Lewis structure and IF3 Molecular Geometry
  • ICl3 Lewis structure and ICl3 Molecular Geometry
  • IBr3 Lewis structure and IBr3 Molecular Geometry
  • ClF5 Lewis structure and ClF5 Molecular Geometry
  • IF5 Lewis structure and IF5 Molecular Geometry
  • PH3 Lewis structure and PH3 Molecular Geometry
  • AsH3 Lewis structure and AsH3 Molecular Geometry
  • AsCl3 Lewis structure and AsCl3 Molecular Geometry
  • AsF3 Lewis structure and AsF3 Molecular Geometry
  • NCl3 Lewis structure and NCl3 Molecular Geometry
  • NF3 Lewis structure and NF3 Molecular Geometry
  • NBr3 Lewis structure and NBr3 Molecular Geometry
  • AlCl3 Lewis structure and AlCl3 Molecular Geometry
  • AlF3 Lewis structure and AlF3 Molecular Geometry
  • AlBr3 Lewis structure and AlBr3 Molecular Geometry
  • CCl4 Lewis structure and CCl4 Molecular Geometry

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