Lewis Structure of OH- (With 6 Simple Steps to Draw!)

Lewis Structure of OH-

I’m super excited to teach you the lewis structure of OH- ion in just 6 simple steps.

Infact, I’ve also given the step-by-step images for drawing the lewis dot structure of OH- ion.

So, if you are ready to go with these 6 simple steps, then let’s dive right into it!

Lewis structure of OH- ion (or hydroxide ion) contains one single bond between the Oxygen (O) atom and Hydrogen (H) atom. The Oxygen atom has three lone pairs and it also has -1 formal charge.

Let’s draw and understand this lewis dot structure step by step.

(Note: Take a pen and paper with you and try to draw this lewis structure along with me. I am sure you will definitely learn how to draw lewis structure of OH-).

6 Steps to Draw the Lewis Structure of OH-

Step #1: Calculate the total number of valence electrons

Here, the given molecule is OH- (hydroxide ion). In order to draw the lewis structure of OH- ion, first of all you have to find the total number of valence electrons present in the OH- ion.
(Valence electrons are the number of electrons present in the outermost shell of an atom).

So, let’s calculate this first.

Calculation of valence electrons in OH-

  • For Oxygen:

Oxygen is a group 16 element on the periodic table.

Hence, the valence electron present in oxygen is 6 (see below image).

  • For Hydrogen: 

Hydrogen is a group 1 element on the periodic table.

Hence, the valence electron present in hydrogen is 1 (see below image).

Hence in a OH- ion, 

Valence electrons given by Oxygen (O) atom = 4
Valence electron given by Hydrogen (H) atom = 1
Electron due to -1 charge, 1 more electron is added
So, total number of Valence electrons in OH- ion= 4 + 1 + 1 = 6

Step #2: Select the center atom (H is always outside)

While selecting the atom, you have to put the least electronegative atom at the center. 

But here in the OH- ion, there are only two atoms. So you can consider any of the atoms as a center atom.

step 1

So, let’s assume that the oxygen atom is a central atom. (Because we have to keep hydrogen outside as per the rule).

Step #3: Put two electrons between the atoms to represent a chemical bond

Now in the above sketch of OH molecule, put the two electrons (i.e electron pair) between the oxygen atom and hydrogen atom to represent a chemical bond between them.

step 2

This pair of electrons present between the Oxygen (O) atom and Hydrogen (H) atom forms a chemical bond, which bonds both the oxygen atom and hydrogen atom with each other in a OH- ion.

Step #4: Complete the octet (or duplet) on outside atom. If the valence electrons are left, then put the valence electrons pair on the central atom

Don’t worry, I’ll explain!

In the Lewis structure of OH- ion, the outer atom is hydrogen atom and it already has a duplet (see below image).

step 3

Also, only 2 valence electrons of OH- ion are used in the above structure.

But there are total 8 valence electrons in OH- ion (as calculated in step #1).

So the number of electrons left to be kept on the central atom = 8 – 2 = 6.

So let’s keep these six electrons (i.e 3 electron pairs) on the oxygen atom.

step 4

Now, let’s move to the next step.

Step #5: Check whether the central atom has octet or not

In this step, we have to check whether the central atom (i.e oxygen) has an octet or not. 

In simple words, we have to check whether the central Oxygen (O) atom is having 8 electrons or not.

step 5

As you can see from the above image, the central atom (i.e oxygen), is having 8 electrons. So it fulfills the octet rule and the oxygen atom is stable.

Step #6: Check the formal charge

Now, you have come to the final step and here you have to check the formal charge on OH molecule. 

For that, you need to remember the formula of formal charge;

Formal charge = Valence electrons – Nonbonding electrons – (Bonding electrons)/2

step 6
  • For Oxygen:
    Valence electrons = 6 (as it is in group 16)
    Nonbonding electrons = 6
    Bonding electrons = 2
  • For Hydrogen:
    Valence electron = 1 (as it is in group 1)
    Nonbonding electrons = 0
    Bonding electrons = 2
Formal charge=Valence electronsNonbonding electrons(Bonding electrons)/2
O=662/2=-1
H=102/2=0

Let’s keep these charges on the atoms in the above lewis structure of OH molecule.

step 7

As you can see in the above sketch, there is one -ve charge on the oxygen atom, which indicates the -1 formal charge on the OH molecule.

Hence, the above lewis structure of OH- ion is the stable lewis structure.

Each electron pair (:) in the lewis dot structure of OH- ion represents the single bond ( | ). So the above lewis dot structure of OH- ion can also be represented as shown below.

OH- Lewis Structure

Related lewis structures for your practice:
Lewis structure of N2H2
Lewis structure of CH3Cl
Lewis structure of HBr
Lewis structure of N2H4
Lewis structure of CH3NH2

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