N2O5 Lewis structure

N2O5 (dinitrogen pentoxide) has two nitrogen atoms and five oxygen atoms.

In the N2O5 Lewis structure, there are two single bonds around the center oxygen atom, with two nitrogen atoms attached to it, and each nitrogen makes one single bond and one double bond with other two oxygen atoms. The oxygen atom with single bonds has three lone pairs, the oxygen atom with double bonds has two lone pairs, and the center oxygen atom also has two lone pairs.

Also, there is a negative (-1) charge on the two oxygen atoms with single bonds, and a positive (+1) charge on the two nitrogen atoms.

Contents

Steps

Use these steps to correctly draw the N2O5 Lewis structure:

#1 First draw a rough sketch
#2 Mark lone pairs on the atoms
#3 Calculate and mark formal charges on the atoms, if required
#4 Convert lone pairs of the atoms, and minimize formal charges
#5 Repeat step 4 if needed, until all charges are minimized, to get a stable Lewis structure

Let’s discuss each step in more detail.

#1 First draw a rough sketch

• First, determine the total number of valence electrons

In the periodic table, nitrogen lies in group 15, and oxygen lies in group 16.

Hence, nitrogen has five valence electrons and oxygen has six valence electrons.

Since N2O5 has two nitrogen atoms and five oxygen atoms, so…

Valence electrons of two nitrogen atoms = 5 × 2 = 10
Valence electrons of five oxygen atoms = 6 × 5 = 30

And the total valence electrons = 10 + 30 = 40

• Second, find the total electron pairs

We have a total of 40 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 = 40 ÷ 2 = 20

• Third, determine the central atom

We have to place the least electronegative atom at the center.

Since nitrogen is less electronegative than oxygen, assume that the central atom is nitrogen.

Here, there are two nitrogen atoms, so we can assume any one as the central atom.

Let’s assume that the central atom is left nitrogen.

Therefore, place nitrogens in the center and oxygens on either side.

• And finally, draw the rough sketch

#2 Mark lone pairs on the atoms

Here, we have a total of 20 electron pairs. And six bonds are already marked. So we have to only mark the remaining fourteen electron pairs as lone pairs on the sketch.

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

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are oxygens and right nitrogen.

So for each top oxygen, left oxygen, and right oxygen, there are three lone pairs. For center oxygen, there are two lone pairs, and for nitrogen, there is zero lone pair because all fourteen electron pairs are over.

Mark the lone pairs on the sketch as follows:

#3 Calculate and mark formal charges on the atoms, if required

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

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

For each nitrogen atom, formal charge = 5 – 0 – ½ (6) = +2

For each top oxygen, left oxygen, and right oxygen atom, formal charge = 6 – 6 – ½ (2) = -1

For center oxygen atom, formal charge = 6 – 4 – ½ (4) = 0

Here, both nitrogen and oxygen atoms have charges, so mark them on the sketch as follows:

The above structure is not a stable Lewis structure because both nitrogen and oxygen atoms have charges. Therefore, reduce the charges (as below) by converting lone pairs to bonds.

#4 Convert lone pairs of the atoms, and minimize formal charges

Convert a lone pair of the top oxygen atom to make a new N — O bond with the left nitrogen atom as follows:

#5 Repeating step 4 to get a stable Lewis structure

Since there are charges on nitrogen and oxygen atoms, again convert a lone pair of the top oxygen atom to make a new N — O bond with the right nitrogen atom as follows:

In the above structure, you can see that the central atom (left nitrogen) forms an octet. And the outside atoms (right nitrogen and oxygens) also form an octet. Hence, the octet rule is satisfied.

Now there are still charges on the atoms. But we can not convert a lone pair to a bond because nitrogen can not keep more than 8 electrons in its last shell.

The formal charges on atoms are closer to zero. Also, the above structure is more stable than the previous structures. Therefore, this structure is the most stable Lewis structure of N2O5.