Lewis Structure of PBr3 | Learn Important Terms and Concepts (2024)

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

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

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

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

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.