HN3 Lewis structure

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HN₃ (hydrazoic acid) has one hydrogen atom and three nitrogen atoms.

In HN₃ Lewis structure, there are two double bonds around the nitrogen atom, with two other nitrogen atoms attached to it, and the left nitrogen is attached with one hydrogen atom. There is one lone pair on the left nitrogen atom, and on the right nitrogen atom, there are two lone pairs.

Also, there is a positive (+1) charge on the center nitrogen atom, and a negative (-1) charge on the right nitrogen atom.

Contents

Steps

Here’s how you can easily draw the HN₃ Lewis structure step by step:

#1 Draw a rough skeleton structure
#2 Mention lone pairs on the atoms
#3 If needed, mention formal charges on the atoms
#4 Minimize formal charges by converting lone pairs of the atoms, and try to get a stable Lewis structure
#5 Repeat step 4 again if needed, until all charges are minimized

Now, let’s take a closer look at each step mentioned above.

#1 Draw a rough skeleton structure

First, determine the total number of valence electrons

In the periodic table, hydrogen lies in group 1, and nitrogen lies in group 15.

Hence, hydrogen has one valence electron and nitrogen has five valence electrons.

Since HN₃ has one hydrogen atom and three nitrogen atoms, so…

Valence electrons of one hydrogen atom = 1 × 1 = 1
Valence electrons of three nitrogen atoms = 5 × 3 = 15

And the total valence electrons = 1 + 15 = 16

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

Second, find the total electron pairs

We have a total of 16 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 = 16 ÷ 2 = 8

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.

Now there are three atoms remaining and all three atoms are nitrogen, so we can assume any one as the central atom.

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

Therefore, place nitrogens in the center and hydrogen outside.

And finally, draw the rough sketch

HN3 Lewis Structure (Step 1) — Rough sketch of HN₃ Lewis structure | Image: Learnool

#2 Mention lone pairs on the atoms

Here, we have a total of 8 electron pairs. And three bonds are already marked. So we have to only mark the remaining five electron pairs as lone pairs 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 nitrogen 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 hydrogen, right nitrogen, and left nitrogen. But no need to mark on hydrogen, because hydrogen already has two electrons.

So for right nitrogen, there are three lone pairs, for left nitrogen, there are two lone pairs, and for center nitrogen, there is zero lone pair because all five electron pairs are over.

Mark the lone pair on the sketch as follows:

HN3 Lewis Structure (Step 2) — Lone pairs marked on HN₃ Lewis structure | Image: Learnool

#3 If needed, mention formal charges on the atoms

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

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

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

For left nitrogen atom, formal charge = 5 – 4 – ½ (4) = -1

For center nitrogen atom, formal charge = 5 – 0 – ½ (4) = +3

For right nitrogen atom, formal charge = 5 – 6 – ½ (2) = -2

Here, all three nitrogen atoms have charges, so mark them on the sketch as follows:

HN3 Lewis Structure (Step 3) — Formal charges marked on HN₃ Lewis structure | Image: Learnool

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

#4 Minimize formal charges by converting lone pairs of the atoms

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

HN3 Lewis Structure (Step 4) — Lone pair of left nitrogen is converted, but still there are charges | Image: Learnool

#5 Since there are charges on atoms, repeat step 4 again

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

HN3 Lewis Structure (Step 5) — Lone pair of right nitrogen is converted again, and got the most stable Lewis structure of HN₃ | Image: Learnool

In the above structure, you can see that the central atom (center nitrogen) forms an octet. The outside atoms (left nitrogen and right nitrogen) also form an octet, and hydrogen forms a duet. Hence, the octet rule and duet rule are satisfied.

Now there is still a positive (+1) charge on the center nitrogen atom, and a negative (-1) charge on the right nitrogen atom.

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 HN₃.

Next: SeOF₂ Lewis structure

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External video

HN3 Lewis Structure (Hydrazoic acid) – Wayne Breslyn

External links

Deep

Learnool.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.