Lewis structure of NH2-

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The Lewis structure of NH₂^– contains two single bonds, with nitrogen in the center, and two hydrogens on either side. There are two lone pairs on the nitrogen atom, and the hydrogen atom does not have any lone pair.

Plus, there is a negative (-1) charge on the nitrogen atom.

Steps

By using the following steps, you can easily draw the Lewis structure of NH₂^–.

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Calculate formal charge and check stability (if octet is already completed on central atom)

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 hydrogen is a group 1 element. Hence, nitrogen has five valence electrons and hydrogen has one valence electron.

Now NH₂^– has one nitrogen atom and two hydrogen atoms.

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

And NH₂^– has a negative (-1) charge, so we have to add one more electron.

Therefore, the total number of valence electrons = 5 + 2 + 1 = 8

• Now decide the central atom

We can not assume hydrogen as 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.

Hence, assume that nitrogen is the central atom.

So now, put nitrogen in the center and hydrogens on either side. And draw the rough skeleton structure for the Lewis structure of NH₂^– something like this:

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

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since nitrogen is surrounded by two hydrogens, use four electrons to show two chemical bonds as follows:

Also read: How to draw Lewis structure of NI₃ (4 steps)

#3 Mark lone pairs

As calculated earlier, we have a total of 8 valence electrons. And in the above structure, we have already used four valence electrons. Hence, four valence electrons are remaining.

Two valence electrons represent one lone pair. So four valence electrons = two lone pairs.

Note that nitrogen is a period 2 element, so it can not keep more than 8 electrons in its last shell. And hydrogen is a period 1 element, so it can not keep more than 2 electrons in its 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 hydrogens. But hydrogen can not keep more than 2 electrons in its last shell. Hence, don’t mark the lone pairs on hydrogen.

So the central atom (nitrogen) will get two lone pairs.

Now draw the Lewis structure of NH₂^– something like this:

In the above structure, you can see that the octet is completed on the central atom (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 ICl₂^– (4 steps)

#4 Calculate formal charge 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 nitrogen atom

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

Formal charge = 5 – 4 – ½ (4) = -1

• For each hydrogen atom

Valence electrons = 1
Nonbonding electrons = 0
Bonding electrons = 2

Formal charge = 1 – 0 – ½ (2) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of NH₂^– 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 NH₂^–.

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

Now NH₂^– is an ion having a negative (-1) charge, so draw brackets around the above Lewis structure and mention that charge on the top right corner. And then, the Lewis structure of NH₂^– looks something like this:

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Related

• Lewis structure of acetone
• Lewis structure of NI₃
• Lewis structure of ICl₂^–
• Lewis structure of HCO₃^–
• Lewis structure of HNO₂

External links

• NH2- Lewis Structure in 6 Steps (With Images) – Pediabay
• NH2 Lewis Structure, Molecular Geometry, Hybridization, and Polarity – Techiescientist
• Drawing the Lewis Structure for NH2 – The Geoexchange
• NH2- Lewis Structure, Molecular Structure, Hybridization, Bond Angle and Shape – Geometry of Molecules
• NH2- lewis structure, molecular geometry, hybridization, bond angle – Topblogtenz
• Why does the Lewis structure for NH2 have 4 dots and not 3? – Chemistry Stack Exchange
• Draw the Lewis structure for NH₂^– and determine the formal charge of each atom – Homework.Study.com
• Which is the correct Lewis dot structure of NH2 – Quora
• Draw the Lewis structure for NH₂^–. Include lone pairs – Chegg
• NH2- Lewis Structure, Molecular Geometry, Polarity & Hybridization – Science Coverage