Lewis structure of OH-

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The Lewis structure of OH^– contains a single bond between the oxygen atom and hydrogen atom. There are three lone pairs on the oxygen atom, and the hydrogen atom does not have any lone pair.

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

Steps

By using the following steps, you can easily draw the Lewis structure of OH^–:

#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… oxygen is a group 16 element and hydrogen is a group 1 element. Hence, oxygen has six valence electrons and hydrogen has one valence electron.

Now OH^– has one oxygen and one hydrogen atom.

So the total number of valence electrons = valence electrons of oxygen atom + valence electrons of hydrogen atom

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

Therefore, the total number of valence electrons = 6 + 1 + 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 oxygen is the central atom.

So now, put oxygen and hydrogen next to each other. And draw the rough skeleton structure for the Lewis structure of OH^– something like this:

Also read: How to draw Lewis structure of SiH₄ (3 steps)

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond as follows:

Also read: How to draw Lewis structure of N₂H₂ (5 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 two valence electrons. Hence, six valence electrons are remaining.

Two valence electrons represent one lone pair. So six valence electrons = three lone pairs.

Note that oxygen 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 atom is hydrogen. 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 (oxygen) will get three lone pairs.

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

In the above structure, you can see that the octet is completed on the central atom (oxygen), and also on the outside atom. 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 NOCl (5 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 oxygen atom

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

Formal charge = 6 – 6 – ½ (2) = -1

• For 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 OH^– 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 OH^–.

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

Now OH^– 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 OH^– looks something like this:

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Related

• Lewis structure of SiH₄
• Lewis structure of N₂H₂
• Lewis structure of NOCl
• Lewis structure of CH₃COOH
• Lewis structure of ClO^–

External links

• Drawing the Lewis Structure for OH- (Hydroxide Ion) – The University of Maryland
• Chemical Bonding: OH- Lewis Structure – The Geoexchange
• OH- Lewis Structure in 6 Steps (With Images) – Pediabay
• Draw the Lewis Dot Structure for the radical hydroxide, OH – Pearson
• How do you write the electron dot diagram for the hydroxide ion OH^–? – Socratic
• What is the Lewis structure for OH – Quora
• Lewis Dot of Hydroxide OH- – Kent’s Chemistry
• Hydroxide Molecule | Definition, Lewis Structure & Ion – Study.com
• OH- lewis structure, molecular geometry, bond angle, hybridization – Topblogtenz
• OH- (Hydroxyl ion) Lewis Structure, Steps of Drawing – Chemistry School
• OH- Lewis Structure: Drawings, Hybridization, Shape, Charges, Pair and Detailed Facts – Lambda Geeks
• Hydroxide – Wikipedia
• Draw the Lewis structure for a hydroxide – Chegg
• How does the Lewis structure of OH- work? – Reddit
• Write Lewis structure for the hydroxide ion, OH – Numerade
• Draw the Lewis structure for a hydroxide – OneClass
• When drawing the correct Lewis structure for the OH- ion, the oxygen atom has – Brainly