Diagram of the H3O+ Lewis structure and geometry as well as hybridization

The hydronium ion is the cation H3O+. In the IUPAC nomenclature, hydronium ion is referred to as oxonium, which makes sense when we look at the ion’s nomenclature.

All three-valent oxygen cations are known by the generic term oxyonium; hence, the specific name hydronium is required to distinguish hydronium ions.

The hydronium ion has a molar mass of 19.02 g/mol.

The protonation of water results in the generation of this ion.

Water and hydrogen ion are combined to form H3O+ (Hydrogen ion).

The pH of water is measured using this ion. OH- and H3O+ can be separated from water and used to measure the pH of the water.

Hydronium ions are utilised in several reactions and chemical synthesis processes. Hexavalent hydronium (Hx) is found in both organic and inorganic systems.

However, we must first understand the fundamentals of this ion, such as its Lewis structure, geometry, and so on, before we can understand how it is used in various processes.

The more we learn about this ion, the more we’ll be able to understand it. To understand any reaction, we should first learn about the compound’s history.

Here are some intriguing facts about hydronium ion that you may not have known before!

Lewis structure of H3O+

Let’s draw the Lewis structure of H3O+ together.

The first step is to figure out how many valence electrons hydronium ion has.

One hydrogen atom is equal to one unit of measure.

How many hydrogen molecules are in three?

6 is the oxygen ionisation constant.

Totaled, there are a total of nine.

As a reminder, the + sign denotes a loss of electrons from the valence electrons. This is the most crucial aspect to remember.

Gaining an electron is indicated by the – symbol.

As a result, there are now a total of 8 valence electrons.

A central atom should be chosen, which is typically the most available for bonding. Oxygen is the central atom in this scenario.

The skeletal structure of H3O+ must therefore be drawn using only single bonds. To complete the lewis structure of H3O+, we must add the remaining electrons to the octet.

Finally, we should make sure that each and every atom in the Lewis structure of H3O+ has its lowest possible formal charge.

The lewis structure of hydronium ion is depicted in the attached figure.

What is the procedure for drawing a Lewis structure?

The structure of a molecule, the types and numbers of bonds, the physical qualities, and the interactions with other compounds may all be gleaned from a lewis structure.

How easy is it to create the lewis structure?

There is a standard technique to depict the Lewis structure of any given molecule. For your convenience, I’ve broken down the instructions below into bullet points:

Determine the molecule’s total number of valence electrons. When performing calculations, be mindful of the + and – signs.

Choose the atom with the most bonding sites as the core atom.

Only use single ties to construct a skeletal structure.

In order to complete the octet of the atoms, you need to add the remaining electrons. Remember to start with the more electronegative atoms and work your way up.

If necessary to complete the atoms’ octet, provide several bonds.

Last but not least, make sure that all of the atoms have the lowest formal charges they may possibly have. The formula for calculating the same is provided below:. –

For the most part, Lewis structure laws apply to all molecules, but there are several notable exceptions. It’s all about the exceptions in chemistry after all!

Hybridization of H3+ with H2

H3O+ (hydronium ion) hybridization is Sp3 (sp3 = sp3+).

Any molecule’s hybridization can be deduced from its formula.

The formula for calculating H is as follows: H = 12


h = hybridization.

V is the number of valence electrons in a molecule.

Number of monovalent atoms (M)

The cation’s charge is C.

anions have a negative charge of A

Sp hybridization occurs if H=2

Sp2 hybridization is achieved by the use of the H3 genetic code.

In this case, H=4 = Sp3 fusion.

H=5 = Sp3d hybridization.

Heterodimerization of Sp3d2

The hybridization of H3O+ can now be determined with the use of this formula.

The core atom in hydronium ion is oxygen, which possesses six valence electrons.

V = 6 as a result of the formula.

The number of monovalent atoms (M) is 3 because 3 hydrogen atoms are linked to oxygen.

C = 1 because it is a cationic molecule.

Therefore, H = 12 [6 + 3 – 1] = 4;

As a result, we can state that H3O+ hybridization is Sp3.

The mixing of atomic orbitals to create a new hybrid orbital is often referred to as “hybridization.”

The VSEPR chart can also be used to determine a molecule’s hybridization, which we’ll cover in the next section.

Molecular Geometry of H3O+.

Trigonal pyramids and tetrahedral electronic geometry characterise the molecular structure of H3O+.

According to the following diagram, hydronium is an AX3E-type molecular structure.

In this example, the central atom, X, is bonded to it, and E is a lone pair.

This means that H3O+ has trigonal pyramid as a molecular form and tetrahedral electron geometry, according to the VSEPR diagram.

All of the foregoing is illustrated in the accompanying image.

It’s now obvious that molecular structure and electronic geometry are distinct entities.

Only the atoms are considered for establishing the molecule’s structure in a molecular shape.

Electron geometry, on the other hand, takes into account all electron pairs.

Instead of considering molecule form, the electron geometry takes lone pairs into account.

Hybridization can also be inferred using the VSEPR chart, as I said earlier. Hydronium ion has Sp3 hybridization as well, as we can see from this image.

The oxygen atom in the H3O+ molecule has a lone pair, which contributes to the polarity.

H3O+ has a net dipole of some non-zero value, making it polar.

Molecular Orbital (MO) Diagram of H3O+

Any molecule’s molecular orbital diagram offers us an indication of the molecule’s orbital mixing.

The overlap diagram of H3O+ is nearly identical to that of H2O, except that it has one fewer electron and one extra hydrogen.

As a point of comparison, the molecular orbital diagrams for H3O+ and H2O are shown in the graphic below.

This graphic shows the MO diagram for hydronium ion on the left-hand side.

The MO is made up of three hydrogen atoms’ atomic orbitals. Furthermore, O+’s atomic orbital has one less electron than water’s.

The molecule’s MO has two electrons in the non-bonding orbital, and these two electrons come together to form it.

The antibonding orbital is empty, whereas the bonding orbital has six electrons.

Additionally, the MO diagram of OH- may be seen in the figure.

We can observe from the molecular orbital diagram that hydronium ion has only sigma bonding, which means that only head-on overlap is feasible.

Ionized hydronium’s molecular orbital diagram is explained in this way.

Using a MO diagram, we may determine the bonding order of a molecule, which in turn provides us with information such as bond length and stability of the compound, among other things.


Hydronium ions are the subject of this article, which focuses on their structure, bonding, and hybridization. The schematic of molecular orbitals is also explained.

Hydronium ion can be used in a variety of ways, as I discussed earlier. In order to better understand the reactions, it is important to learn the fundamentals. Everything else about hydronium ions will make sense after that.

Let me know if this article was of use to you in any way, and what you learned from it!

Please feel free to contact me with any questions or concerns you may have, and enjoy your reading!

Read more: Acidic or alkaline is milk’s pH?

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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