Polarity, Lewis Structure, Molecular Geometry, and Hybridization of SO42

Sulfate ion (SO42-) is one of the most often encountered ions in chemistry. This is a polyatomic anion with a -2 electronegativity.

MgSO4, CaSO4, Na2SO4, and PbSO4 are examples of well-known sulphate compounds. Sulfates can be easily produced by oxidising metal sulfites and sulphides. We may also utilise sulfuric acid and metals to obtain the sulphate salts we seek.

Zn + H2SO4 ——> H2 + ZnSO4 (Here, zinc sulphate is produced by combining zinc metal with sulfuric acid.)

Since we can easily obtain this ion, whether naturally or synthetically, it assists us in more ways than you may imagine in our daily lives.

Sulfate compounds are utilised everywhere, from body and hygiene-care items like toothpaste, shampoos, soaps, and detergents to water treatment techniques.

Sulfates have downsides, despite the fact that they can be employed in a variety of applications.

It has a significant role in the composition of acid rain. In addition, it has been determined that sulphur indirectly contributes to cooling effects and global dimming.

We must study the chemical bonding and extra properties of SO42- to have a greater understanding of nature and atomic reactions.

SO42 Lewis Architecture

According to the internal structure of a molecule, we know that it is made up of atoms, which are constituted of a nucleus and electrons.

Electrons, negatively charged particles, surround the atomic nucleus in shells.

When discussing chemical bonding using the Lewis Structure idea, the electrons of the outermost shell, i.e. valence shell electrons, are represented as dots, while the bonds established between atoms are represented as straight lines.

As a result, the Lewis Structure is also known as the electron dot structure, and it is one of the most prevalent and straightforward notions for comprehending the chemical bonding of molecular compounds.

Here, we shall work with the sulphate ion, represented by the symbol SO42-.

Step 1: Determine the total amount of valence electrons in the molecule or ion.

One molecule of sulphur and four molecules of oxygen compose sulphate ions.

Sulfur and oxygen both have six valence electrons and belong to the same group in the periodic table (the chalcogen family).

Total valence electrons in SO42- are equal to 61 + 64 + 2 = 32.

Due to the negative 2-charge on the sulphate ion, two electrons had to be added.

Step two: Identify the core atom

To determine the molecule’s core atom, we must consider electronegativity.

Electronegativity quantifies an atom’s propensity to attract negatively charged electrons in order to form anionic compounds.

In this case, oxygen is more electronegative than sulphur. Consequently, sulphur is the central atom.

Draw the skeleton diagram of the molecule in Step 3.

We will now sketch the skeletal diagram of the sulphate ion using atomic symbols and dot line structures.

Here, the symbols for sulphur and oxygen are notated, and the valence electrons are represented by dots.

Step four: examine the Octet rule

Atoms contained in the major groups of the periodic table have an average valency of eight, similar to noble gases such as argon, xenon, etc.

When atoms of different types join to create molecules, they adhere to the octet rule.

As shown in the image above, the five molecules have completed their octet configuration and the total number of valence electrons remains 32. By drawing single bonds, we obtain the following structure:

Formal Charge Calculation (Step 5)

The following diagram may lead us to believe that we have found the ideal Lewis Structure, however there is still one more step.

We must calculate the formal charge to determine if all constituent atoms have the minimum formal charge values feasible.

To accomplish this, we must apply the following formula:

Formal Charge= Valence Electrons- Lone pair electrons- 0.5* Bonded Electrons

Each oxygen atom has a formal charge equal to 6- 6- 0.5*2 = -1.

Formal charge for the sulphur atom equals 6-0-0.5*8 = +2

We must reduce the amount of formal charge values. Thus, a single bond is insufficient. We must establish double bonds.

Considering double bonds in two of the sulfur-oxygen pairings yields the structure shown below.

Now, if we examine the formal charges, we discover that the formal charge for sulphur is zero, that of the oxygen atoms with double bonds is zero, and that of the oxygen atoms with single bonds is -1.

Now we have the ideal Lewis structure!

Next, we will discuss Molecular Geometry.

SO42 Molecular Geometry

After deducing the best feasible Lewis Structure diagram for a given molecule, we must go deeper and determine how our molecule can appear in a plane!

Molecular geometry provides a three-dimensional picture of how atoms are connected and at what angles, as well as a wealth of information on the subject.

To determine the molecular structure of SO42-, we must examine the VSEPR theory, which is an abbreviation for Valence Shell Electron Pair Repulsion Theory.

We reduce the repulsion between negatively charged electron clouds surrounding constituent atomic nuclei using the VSEPR model.

Consider the expression AXN:

Here, A represents the core atom, sulphur.

X represents the number of atoms bound to sulphur, which is 4 in this case (four oxygen atoms around the centre S). N represents the bonding and non-bonding pairs of electrons.

When we evaluate A and X in this case, the resulting formula is AX4.

Consequently, the chart reveals that SO42- has a tetrahedral structure. The bond angles are quite close to 109.50 degrees.

Here is an exact three-dimensional illustration of the sulphate ion’s molecular form.

SO42 Hybridization

Hybridization is a fundamental notion of chemical bonding that will be useful whenever we need to discuss a molecule or learn about its properties.


The theory of hybridization describes the fusion and combination of atomic orbitals with similar energy levels to generate hybridised orbitals. Depending on the orbital overlap, molecules such as sp, sp2, sp3, and so on exhibit various hybridizations.

In the case of sulphate ions, the hybridization must be determined in order to comprehend the overlap of orbitals.

This may be determined with a fairly easy formula:


Here, H represents the hybridization type

V denotes the amount of valence electrons surrounding the centre atom.

M stands for monovalent atoms

A and C represent the anionic and cationic charges contained within a molecule, respectively.

V=6 for sulphate ion, M=0, A=2 and C=0

Therefore, the H value is:

H= 0.5(6+0+2-0) = 4

This represents an sp3 hybridization.

Sulphur’s electronic configuration is:

S= [Ne] 3s23p4

If we broaden this we get:

S= [Ne] 3s2 3px2 3py1 3pz1 3d0

If we separate then we get,

S=[Ne] 3s1 3px1 3pz1 3py1 3dxy1 3dyz1

In this instance, the s and p orbitals mix and merge to generate the sp3 hybridization, whilst the d orbitals remain unhybridized.

SO42 Polarization


Polarity is the concept pertaining to dipole moments and differences in electronegativities (at least 0.5) within a molecule or ion.

This indicates that if a chemical comprises atoms with varying electronegativity values, i.e. an asymmetrical electronic distribution, it is typically polar. A polar molecule possesses partial positive and negative charges (+ and -) on its inside.

We measure polarity using a concept known as the dipole moment.

The polarity of the ion Sulfate

Do you aware that SO42- ion is capable of resonance?

As seen in the diagram, six resonance configurations exist for sulphate.

We’ve already discovered the ideal Lewis Structure and confirmed that the molecule form is tetrahedral.

There are no poles in SO42- since its structure is symmetrical.

However, this does not indicate that there is no ultimate charge, as this ion has a double negative charge.

Despite being non-polar, this ion tends to react with other polar substances. This occurs because the charged molecule interacts with the partial charge present in any polar component, such as H2O. ( water).


The sulphate ion present in naturally occurring and industrially produced salts is an essential chemical component that we must master. We have encountered and will continue to encounter numerous substances that include sulphate ions. In order to comprehend the probable reactions and physical and chemical properties of the relevant compounds, it is required to have some knowledge of this topic. Chemical bonding enables us to have a clear and comprehensive understanding of atomic components.

SO42-‘s Lewis Structure, Molecular Geometry, Hybridization type, and Polarity have been exhaustively discussed in this page. This will make learning about sulphate ion much simpler!

Read more: Lewis Structure, Hybridization, Polarization, and Molecular Geometry of Compound PO43

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


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