H3O+ Lewis structure

H₃O⁺ (hydronium) has three hydrogen atoms and one oxygen atom.

In the H₃O⁺ Lewis structure, there are three single bonds around the oxygen atom, with three hydrogen atoms attached to it, and on the oxygen atom, there is one lone pair.

Also, there is a positive (+1) charge on the oxygen atom.

Alternative method: Lewis structure of H₃O⁺

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, hydrogen lies in group 1, and oxygen lies in group 16.

Hence, hydrogen has one valence electron and oxygen has six valence electrons.

Since H₃O⁺ has three hydrogen atoms and one oxygen atom, so…

Valence electrons of three hydrogen atoms = 1 × 3 = 3
Valence electrons of one oxygen atom = 6 × 1 = 6

Now the H₃O⁺ has a positive (+1) charge, so we have to subtract one electron.

So the total valence electrons = 3 + 6 – 1 = 8

Learn how to find: Hydrogen valence electrons and Oxygen valence electrons

• Second, find the total electron pairs

We have a total of 8 valence electrons. And when we divide this value by two, we get the value of total electron pairs.

Total electron pairs = total valence electrons ÷ 2

So the total electron pairs = 8 ÷ 2 = 4

• Third, determine the central atom

Here hydrogen can not be the central atom. Because the central atom is bonded with at least two other atoms, and hydrogen has only one electron in its last shell, so it can not make more than one bond.

Hence, here we have to assume that the central atom is oxygen.

Therefore, place oxygen in the center and hydrogens on either side.

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 4 electron pairs. And three O — H bonds are already marked. So we have to only mark the remaining one electron pair as a lone pair on the sketch.

Also remember that hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell. And oxygen is a period 2 element, so it can not keep more than 8 electrons in its last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are hydrogens. But no need to mark on hydrogen, because each hydrogen has already two electrons.

So for oxygen, there is one lone pair.

Mark the lone pair on the sketch as follows:

Formal charge

Use the following formula to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

For each hydrogen atom, formal charge = 1 – 0 – ½ (2) = 0

For oxygen atom, formal charge = 6 – 2 – ½ (6) = +1

Here, the oxygen atom has a charge, so mark it on the sketch as follows:

Final structure

The final structure of H₃O⁺ features a central oxygen atom connected to three hydrogen atoms through single covalent bonds. In this configuration, the oxygen atom satisfies the octet rule by maintaining one lone pair alongside its three bonding pairs. Each hydrogen atom reaches its stable duet state through its shared pair of electrons. This arrangement results in a formal charge of +1 on the oxygen atom, while each hydrogen atom has a formal charge of zero. Consequently, this specific electronic distribution serves as the definitive and most accurate Lewis representation of the hydronium ion.

To complete the representation, draw square brackets around the entire Lewis structure and place a “+” or “+1” sign as a superscript outside the upper right bracket. This notation signifies that the positive charge is a property of the whole ion, resulting from the loss of one electron from the collective group of atoms.

Next: CH₃NO₂ Lewis structure

External video

• A step-by-step explanation of how to draw the H3O+ Lewis Structure – YouTube • Wayne Breslyn

External links

• https://lambdageeks.com/h3o-lewis-structure/
• https://techiescientist.com/h3o-lewis-structure/
• https://www.chemistryscl.com/general/H3O%2B-lewis-structure/
• https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/H3OPlus-lewis-structure.html