HN3 Lewis structure

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.

Alternative method: Lewis structure of HN₃

Contents

Rough sketch

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

Lone pair

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

Formal charge

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.

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

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

Final structure

The final structure of HN₃ includes a linear chain of three nitrogen atoms with a hydrogen atom attached to one end. In this configuration, the hydrogen atom forms a single bond with the first nitrogen, which in turn is connected to the central nitrogen atom by a double bond. The central nitrogen is then linked to the terminal nitrogen atom by another double bond. Both the terminal nitrogen and the nitrogen bonded to hydrogen retain two lone pairs, while the central nitrogen atom possesses no lone pairs, satisfying the octet rule for all nitrogen atoms and the duet rule for hydrogen. This arrangement is the most stable because it optimizes the formal charge distribution; the central nitrogen carries a formal charge of +1, the terminal nitrogen carries a formal charge of -1, and the remaining atoms carry a charge of zero. Thus, this specific electronic distribution serves as the definitive and most accurate Lewis representation of hydrazoic acid.

Next: SeOF₂ Lewis structure

External video

HN3 Lewis Structure (Hydrazoic acid) – YouTube • 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.