Lewis Structure of OPBr3 (With 6 Simple Steps to Draw!)

I’m super excited to teach you the lewis structure of OPBr3 in just 6 simple steps.

Infact, I’ve also given the step-by-step images for drawing the lewis dot structure of OPBr3 molecule.

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

Lewis structure of OPBr3 contains 1 double bond between the Phosphorus (P) & Oxygen (O) atom and 3 single bonds between the Phosphorus (P) atom & each Bromine (Br) atom. The Phosphorus atom (P) is at the center and it is surrounded by 1 Oxygen atom (O) and 3 Bromine atoms (Br). The Oxygen atom (O) has 2 lone pairs while the Bromine atom (Br) has 3 lone pairs.

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 OPBr3).

6 Steps to Draw the Lewis Structure of OPBr3

Step #1: Calculate the total number of valence electrons

Here, the given molecule is OPBr3. In order to draw the lewis structure of OPBr3, first of all you have to find the total number of valence electrons present in the OPBr3 molecule.
(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 OPBr3

• 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 Phosphorus: 

Phosphorus is a group 15 element on the periodic table.

Hence, the valence electrons present in phosphorus is 5 (see below image).

• For Bromine:

Bromine is a group 17 element on the periodic table.

Hence, the valence electrons present in bromine is 7 (see below image).

Hence in a OPBr3 molecule, 

Valence electrons given by Oxygen (O) atom = 6
Valence electrons given by Phosphorus (P) atom = 5
Valence electrons given by each Bromine (Br) atom = 7
So, total number of Valence electrons in OPBr3 molecule = 6 + 5 + 7(3) = 32

Step #2: Select the center atom

While selecting the center atom, always put the least electronegative atom at the center.

(Remember: Fluorine is the most electronegative element on the periodic table and the electronegativity decreases as we move right to left in the periodic table as well as top to bottom in the periodic table). ^[1]

Here in the OPBr3 molecule, if we compare the oxygen atom (O), phosphorus atom (P) and bromine atom (Br), then phosphorus is less electronegative than bromine and oxygen.

So, phosphorus should be placed in the center and the remaining 3 bromine atoms and 1 oxygen atom will surround it.

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

Now in the above sketch of OPBr3 molecule, put the two electrons (i.e electron pair) between the phosphorus atom, oxygen atom and bromine atom to represent a chemical bond between them.

These pairs of electrons present between the Phosphorus (P), Oxygen (O) and Bromine (Br) atoms form a chemical bond, which bonds these atoms with each other in a OPBr3 molecule.

Step #4: Complete the octet (or duplet) on outside atoms. 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 OPBr3, the outer atoms are oxygen atom and bromine atoms.

So now, you have to complete the octet on these oxygen and bromine atoms (because oxygen and bromine requires 8 electrons to have a complete outer shell).

Now, you can see in the above image that the oxygen and bromine atoms form an octet.

Also, all the 32 valence electrons of OPBr3 molecule (as calculated in step #1) are used in the above structure. So there are no remaining electron pairs.

Hence there is no change in the above sketch of OPBr3.

Let’s move to the next step.

Step #5: Check whether the central atom has octet or not. If it does not have an octet, then move the electron pair from the outer atom to form a double bond or triple bond

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

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

As you can see from the above image, the central atom (i.e phosphorus), has 8 electrons. So it fulfills the octet rule.

Step #6: Final step – Check the stability of lewis structure by calculating the formal charge on each atom

Now, you have come to the final step and here you have to check the formal charge on phosphorus atom (P), oxygen atom (O) as well as each bromine atom (Br).

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

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

• For Phosphorus:
  Valence electrons = 5 (as it is in group 15)
  Nonbonding electrons = 0
  Bonding electrons = 8
• For Oxygen:
  Valence electron = 6 (as it is in group 16)
  Nonbonding electrons = 6
  Bonding electrons = 2
• For Bromine:
  Valence electron = 7 (as it is in group 17)
  Nonbonding electrons = 6
  Bonding electrons = 2

Formal charge	=	Valence electrons	–	Nonbonding electrons	–	(Bonding electrons)/2
P	=	5	–	0	–	8/2	=	+1
O	=	6	–	6	–	2/2	=	-1
Br	=	7	–	6	–	2/2	=	0

So you can see above that the formal charges on phosphorus is +1 and the formal charge on the oxygen atom is -1.

This indicates that the above lewis structure of OPBr3 is not stable and so we have to minimize the charges to get a more stable lewis structure.

This can be done by shifting the lone pair from negatively charged oxygen atom to the positively charged phosphorus atom to form a double bond.

Now, in the above structure, you can see that the charges are minimized and the above lewis structure of OPBr3 is the final stable structure.

Each electron pair (:) in the lewis dot structure of OPBr3 represents the single bond ( | ). So the above lewis dot structure of OPBr3 can also be represented as shown below.

Related lewis structures for your practice:
Lewis Structure of PH2-
Lewis Structure of NS2
Lewis Structure of SiH2O
Lewis Structure of OF3-
Lewis Structure of PH4+ 

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