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Lewis Structure of PBr3

Last updated date: 25th Feb 2024
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Lewis Structure of PBr3: An Overview

In PBr3, phosphorus has five valence electrons in its valence shell, out of these five electrons, three form sigma bonds with three bromine atoms and two electrons remain on the phosphorus atom as a lone pair of electrons. Hence, the hybridization of PBr3 is sp3 and the geometry will be trigonal pyramidal due to the presence of a lone pair of electrons on the central atom. Since the geometry is asymmetrical, the molecule will be polar. PBr3 has 26 valence electrons of which bromine atoms can consume eight each in bonding pairs and two electrons in lone pairs on phosphorus. In the Lewis structure of PBr3, the formal charge on the terminal bromine atom is zero.

Lewis Structure of PBr3

The Lewis structure of PBr3 contains three sigma bonds between phosphorus and three bromine atoms. The phosphorus is at the centre and it is surrounded by bromine atoms. The phosphorus has one lone pair of electrons and bromine atoms have three lone pairs of electrons. The hybridization of PBr3 is sp3. Hence, the electron geometry will be tetrahedral because the phosphorus atom has one lone pair and three bonded pairs with bromine atoms. So, there are four regions of electron density around the central atom. But it has a trigonal pyramidal shape or geometry due to the presence of lone pairs on the central atom. The Lewis structure of this molecule is given below.

Lewis Structure of PBr3

Lewis Structure of PBr3

The above image shows the Lewis structure of PBr3. Phosphorus is attached to three bromine atoms by sigma bonds and one lone pair can be seen on the phosphorus atom.

Phosphorus Lewis Structure

The atomic number of the phosphorus atom is 15 and the electronic configuration is as follows: 1s2 2s2 2p6 3s2 3p3

It is clear from the electronic configuration that phosphorus has five valence electrons. Hence, the Lewis dot structure of phosphorus can be drawn by showing electrons on phosphorus atoms as dots. The Lewis dot structure of phosphorus is as follows:

Lewis Structure of Phosphorus

Lewis Structure of Phosphorus

Above image is the Lewis structure of phosphorus. It can be seen that there are five electrons on the Phosphorus atom.

Bond Angle of PBr3

The bond pair-bond pair repulsion increases more than the lone pair-bond pair repulsion when going down a group. So, due to bond pair-bond pair repulsion, the bromine bond angle is more than chlorine.

Since PBr3 is formed by a trigonal pyramidal geometry. The bond angle between Phosphorus and each bromine atom will be 101 degrees.

Bond Angle in PBr3

Bond Angle in PBr3

The above image shows the bond angle between phosphorus and bromine atoms which is 101 degrees in phosphorus and each bromine atom.

PBr3 Name

The name of PBr3 is phosphorus tribromide or tribromo phosphine.

PBr3 Lewis Structure Molecular Geometry

For PBr3, the central atom is phosphorus, three bromine atoms form bonds with it and it has one modified shape to trigonal pyramidal geometry. The molecular geometry of lone pairs of electrons give rise to an sp3 hybridization and form tetrahedral geometry.

Trigonal pyramidal geometry is also shown by molecules which have four atoms or ligands. The central atom will be the apex and three other atoms or ligands will be at one base, where they are in the three corners of the triangle. There is one lone pair of electrons on the central atom.

Lewis Dot Structure of PBr3

In the Lewis dot structure of PBr3, the phosphorus atom has a total of eight electrons. Six electrons are shared between phosphorus and each bromine atom and the remaining two electrons are present on phosphorus atoms as lone pairs of electrons. Each bromine atom has three lone pairs of electrons and two shared electrons between phosphorus and bromine.

Lewis Dot Structure of PBr3

Lewis Dot Structure of PBr3

The above image is the Lewis structure of PBr3. In the structure, the phosphorus atom is bonded with three bromine atoms and has a lone pair.

Key Features of Lewis Structure of PBr3

  • Lewis structures extend the concept of the electron dot structure by adding lines between atoms to represent shared pairs in a chemical bond.

  • Trigonal pyramidal geometry results from tetrahedral electron pair geometry when a lone pair is present on the central atom.

  • The Lewis structure PBr3 has trigonal pyramidal shape according to its molecular geometry and tetrahedral shape according to its electron geometry.

  • The trigonal pyramidal molecule is symmetrical about the central atom.

  • For trigonal pyramidal geometry, the bond angle is slightly less than 109.5 degrees.

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FAQs on Lewis Structure of PBr3

1. How is PBr3 formed? 

PBr3 is prepared by treating red phosphorus with bromine. Excess phosphorus is used in order to prevent formation of PBr5.

2. What does PBr3 do as a reagent?

In Hell-volhard-zelinsky halogenation, phosphorus tribromide is usually used for the bromination of carboxylic acids to form the corresponding acyl bromide. It also can be used to convert primary and secondary alcohols to alkyl bromides.

3. How does PBr3 act in the formation of alkyl halides?

Alcohol is changed into a leaving group when alkyl bromide is produced using PBr3 by linking with phosphorus and replacing bromine from phosphorus during the activation stage.

4. Does PBr3 work on carboxylic acids?

The process, which produces acid bromide and HBr, is started by the reaction between carboxylic acid and PBr3. Acid bromide production is crucial to this reaction because it makes alpha bromination possible. This is because they lack the acidic carboxylic acid proton and may enolize much more quickly.