Lewis structure of N2O3

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The Lewis structure of N₂O₃ contains two single bonds and two double bonds, with two nitrogens in the center. The left nitrogen is attached with two oxygens, and the right nitrogen is attached with one oxygen. The left oxygen atom and right oxygen atom have two lone pairs, the top oxygen atom has three lone pairs, and the right nitrogen atom has one lone pair.

Plus, there is a positive (+1) charge on the left nitrogen atom, and a negative (-1) charge on the top oxygen atom.

Steps

By using the following steps, you can easily draw the Lewis structure of N₂O₃.

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Complete octet on atoms by calculating formal charge
#5 Calculate formal charge again and check stability

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

• Let’s calculate the total number of valence electrons

We know that… nitrogen is a group 15 element and oxygen is a group 16 element. Hence, nitrogen has five valence electrons and oxygen has six valence electrons.

Now N₂O₃ has two nitrogen atoms and three oxygen atoms.

So the total number of valence electrons = (valence electrons of nitrogen atom × 2) + (valence electrons of oxygen atom × 3)

Therefore, the total number of valence electrons = 10 + 18 = 28

• Now decide the central atom

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for nitrogen and oxygen as follows:

Electronegativity value of nitrogen = 3.04
Electronegativity value of oxygen = 3.44

Obviously, nitrogen is less electronegative than oxygen. Hence, assume that left nitrogen is the central atom (as there are two nitrogens).

So now, put two nitrogens in the center and three oxygens on either side. And draw the rough skeleton structure for the Lewis structure of N₂O₃ something like this:

Also read: How to draw Lewis structure of H₂PO₄^– (5 steps)

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since two nitrogens are surrounded by three oxygens, use eight electrons to show four chemical bonds as follows:

#3 Mark lone pairs

As calculated earlier, we have a total of 28 valence electrons. And in the above structure, we have already used eight valence electrons. Hence, twenty valence electrons are remaining.

Two valence electrons represent one lone pair. So twenty valence electrons = ten lone pairs.

Note that both (nitrogen and oxygen) are the period 2 elements, so they can not keep more than 8 electrons in their last shell.

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atoms are oxygens and right nitrogen, so each oxygen will get three lone pairs, and right nitrogen will get one lone pair. And the central atom (left nitrogen) will not get any lone pair, because all ten lone pairs are used.

So the Lewis structure of N₂O₃ looks something like this:

In the above structure, you can see that the octet is completed on outside atoms (except right nitrogen). Also, the central atom (left nitrogen) doesn’t form an octet.

So in the next step, we have to complete the octet on left nitrogen and right nitrogen.

Also read: How to draw Lewis structure of C₂H₂O (5 steps)

#4 Complete octet on atoms by calculating formal charge

Remember that nitrogen is a period 2 element, so it can not keep more than 8 electrons in its last shell.

Now both (left nitrogen and right nitrogen) already have six valence electrons. Hence, both nitrogens need two more valence electrons to complete their octet.

Which means that we have to convert two lone pairs. But the question is, which lone pair should we convert to get the best Lewis structure?

There are two possible ways we can convert lone pair:

1) Convert one lone pair from the left oxygen atom, and one lone pair from either the right oxygen atom or top oxygen atom.
2) Convert one lone pair from the right nitrogen atom, and one lone pair from any one of the oxygen atoms.

The best way to predict which lone pair should be converted to get the best Lewis structure is by calculating formal charges.

The following formula is used to calculate the formal charges on atoms:

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

Collect the data from the above structure and then, write it down below as follows:

• For left nitrogen atom

Valence electrons = 5
Nonbonding electrons = 0
Bonding electrons = 6

Formal charge = 5 – 0 – ½ (6) = +2

• For right nitrogen atom

Valence electrons = 5
Nonbonding electrons = 2
Bonding electrons = 4

Formal charge = 5 – 2 – ½ (4) = +1

• For each oxygen atom

Valence electrons = 6
Nonbonding electrons = 6
Bonding electrons = 2

Formal charge = 6 – 6 – ½ (2) = -1

Mention the formal charges of atoms on the structure. So the Lewis structure of N₂O₃ looks something like this:

In order to get the best Lewis structure, we have to make the formal charges on atoms closer to zero. And we can do so by choosing the 1).

So convert one lone pair from the left oxygen atom to make a new bond with the left nitrogen atom, and one lone pair from the right oxygen atom to make a new bond with the right nitrogen atom.

And then, the Lewis structure of N₂O₃ looks something like this:

In the above structure, you can see that the octet is completed on the central atom (left nitrogen), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

Also read: How to draw Lewis structure of HPO₄^2- (5 steps)

#5 Calculate formal charge again and check stability

The following formula is used to calculate the formal charges on atoms:

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

Collect the data from the above structure and then, write it down below as follows:

• For left nitrogen atom

Valence electrons = 5
Nonbonding electrons = 0
Bonding electrons = 8

Formal charge = 5 – 0 – ½ (8) = +1

• For right nitrogen atom

Valence electrons = 5
Nonbonding electrons = 2
Bonding electrons = 6

Formal charge = 5 – 2 – ½ (6) = 0

• For top oxygen atom

Valence electrons = 6
Nonbonding electrons = 6
Bonding electrons = 2

Formal charge = 6 – 6 – ½ (2) = -1

• For left oxygen and right oxygen atom

Valence electrons = 6
Nonbonding electrons = 4
Bonding electrons = 4

Formal charge = 6 – 4 – ½ (4) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of N₂O₃ looks something like this:

In the above structure, you can see that the formal charges of atoms are closer to zero. Therefore, this is the most stable Lewis structure of N₂O₃.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

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Related

• Lewis structure of H₂PO₄^–
• Lewis structure of C₂H₂O
• Lewis structure of HPO₄^2-
• Lewis structure of C₆H₁₂
• Lewis structure of POF₃

External links

• Lewis Structure of N2O3 (Dinitrogen trioxide) – Chemistry School
• N2O3 Lewis Structure in 5 Steps (With Images) – Pediabay
• Chemical Bonding: N2O3 Lewis Structure – The Geoexchange
• Lewis structure of dinitrogen trioxide – Chemistry Stack Exchange
• Need help on the Lewis structure of N2O3 – Reddit
• What is the lewis structure of N2O3? – Brainly
• What is N2O3 hybridization structure? – Quora
• Draw lewis diagrams of all possible resonance structures of N2O3 – Chegg
• Dinitrogen Trioxide | N2O3 Formula, Oxidation Number & Molar Mass – Study.com
• N2O3 (Dinitrogen Trioxide) Oxidation Number – ChemicalAid
• Predict a possible Lewis structure(s) for N2O3 – Numerade