Lewis Structure of H3O+ (With 6 Simple Steps to Draw!)

Ready to learn how to draw the lewis structure of H3O+ ion?

Awesome!

Here, I have explained 6 simple steps to draw the lewis dot structure of H3O+ ion (along with images).

So, if you are ready to go with these 6 simple steps, then let’s dive right into it!

Lewis structure of H3O+ ion (Hydronium ion) contains three single bonds between the Oxygen (O) atom and each Hydrogen (H) atom. The Oxygen atom (O) is at the center and it is surrounded by 3 Hydrogen atoms (H). The Oxygen atom has one lone pair and it also has +1 formal charge.

Let’s draw and understand this lewis dot structure step by step.

(Note: Take a pen and paper with you and try to draw this lewis structure along with me. I am sure you will definitely learn how to draw lewis structure of H3O+ ion).

6 Steps to Draw the Lewis Structure of H3O+ ion

Step #1: Calculate the total number of valence electrons

Here, the given ion is H3O+ ion (hydronium ion). In order to draw the lewis structure of H3O+, first of all you have to find the total number of valence electrons present in the H3O+ ion.
(Valence electrons are the number of electrons present in the outermost shell of an atom).

So, let’s calculate this first.

Calculation of valence electrons in H3O+ ion

• For Hydrogen: 

Hydrogen is a group 1 element on the periodic table. ^[1]

Hence, the valence electron present in hydrogen is 1 (see below image).

• For Oxygen:

Oxygen is a group 16 element on the periodic table. ^[2]

Hence, the valence electron present in oxygen is 6 (see below image).

Hence in a H3O+ ion,
Valence electron given by each Hydrogen (H) atom = 1
Valence electrons given by Oxygen (O) atom = 6
The +1 charge indicates that one electron is less
So, total number of Valence electrons in H3O+ ion = 1(3) + 6 – 1 = 8

Step #2: Select the center atom (H is always outside)

While selecting the center atom, always put the least electronegative atom at the center.

(Remember: Fluorine is the most electronegative element on the periodic table and the electronegativity decreases as we move right to left in the periodic table as well as top to bottom in the periodic table). ^[3]

Here in the H3O, if we compare the oxygen atom (O) and hydrogen atom (H), then hydrogen is less electronegative than oxygen. But as per the rule, we have to keep hydrogen outside.

So, oxygen should be placed in the center and the remaining 3 hydrogen atoms will surround it.

Step #3: Put two electrons between the atoms to represent a chemical bond

Now in the above sketch of H3O molecule, put the two electrons (i.e electron pair) between each oxygen atom and hydrogen atom to represent a chemical bond between them.

These pairs of electrons present between the Oxygen (O) and Hydrogen (H) atoms form a chemical bond, which bonds the oxygen and hydrogen atoms with each other in a H3O molecule.

Step #4: Complete the octet (or duplet) on outside atoms. If the valence electrons are left, then put the valence electrons pair on the central atom

Don’t worry, I’ll explain!

In the Lewis structure of H3O, the outer atoms are hydrogen atoms.

So now, you have to check whether these hydrogen atoms are forming a duplet or not! (because hydrogen requires only 2 electrons to have a complete outer shell).

You can see in the above image that all the hydrogen atoms form a duplet.

Also, only 6 valence electrons of H3O+ ion are used in the above structure.

But there are total 8 valence electrons in H3O+ ion (as calculated in step #1).

So the number of electrons left to be kept on the central atom = 8 – 6 = 2.

So let’s keep these two electrons (i.e electron pair) on the central atom.

Now, let’s move to the next step.

Step #5: Check whether the central atom has octet or not. If it does not have an octet, then move the electron pair from the outer atom to form a double bond or triple bond

In this step, we have to check whether the central atom (i.e oxygen) has an octet or not. 

In simple words, we have to check whether the central Oxygen (O) atom is having 8 electrons or not.

As you can see from the above image, the central atom (i.e oxygen), has 8 electrons. So it fulfills the octet rule and the oxygen atom is stable.

Step #6: Final step – Check the stability of lewis structure by calculating the formal charge on each atom

Now, you have come to the final step and here you have to check the formal charge on the oxygen atom (O) as well as each hydrogen atom (H).

For that, you need to remember the formula of formal charge;

Formal charge = Valence electrons – Nonbonding electrons – (Bonding electrons)/2

• For Oxygen:
  Valence electrons = 6 (as it is in group 16)
  Nonbonding electrons = 2
  Bonding electrons = 6
• For Hydrogen:
  Valence electron = 1 (as it is in group 1)
  Nonbonding electrons = 0
  Bonding electrons = 2

Formal charge	=	Valence electrons	–	Nonbonding electrons	–	(Bonding electrons)/2
O	=	6	–	2	–	6/2	=	+1
H	=	1	–	0	–	2/2	=	0

Let’s keep these charges on the atoms in the above lewis structure of H3O molecule.

As you can see in the above sketch, there is one +ve charge on the oxygen atom, which indicates the +1 formal charge on the H3O molecule.

Hence, the above lewis structure of H3O+ ion is the stable lewis structure.

Each electron pair (:) in the lewis dot structure of H3O+ ion represents the single bond ( | ). So the above lewis dot structure of H3O+ ion can also be represented as shown below.

Related lewis structures for your practice:
Lewis Structure of CH3NO2
Lewis Structure of AsH3
Lewis Structure of SeF6
Lewis Structure of AsF3
Lewis Structure of KrF2 

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