PCl3 is a POLAR molecule because the Chlorine (Cl) present in the molecule is more electronegative, which causes the partial positive (ẟ+) and partial negative (ẟ-) charge to appear on the molecule. These ẟ+ and ẟ- charges are responsible to make the entire PCl3 molecule polar.
Let me explain this in detail with the help of PCl3 lewis structure and its 3D geometry.
Answer and Explanation:
PCl3 is polar because VSEPR theory predicts the molecular geometry is trigonal pyramidal.
The Lewis structure of PCl3 is:
Four regions of electron density are around phosphorus. One of them is a lone pair of electrons. Generally, a lone pair of electrons on the central atom indicates the molecule is polar.
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Preparation and reaction of PCl3
Phosphorus trichloride(PCl3) is a bright yellowish liquid with a strong intense odor. It is created primarily through the chlorination of phosphorus. It is the heterogeneous reaction, phosphorus in the soft solid phase and chlorine in the gas phase. Initially, phosphorus reacted with chlorine gas formed phosphorus trichloride(PCl3).
It is an exothermic reaction. The chemical equation of phosphorus chlorination exothermic reaction is shown below.
Reaction of PCl3:
What are PCl3 electron and molecular geometry?
PCl3 has a tetrahedral pyramidal or trigonal pyramidal molecular geometry and ammonia like electron geometry, according to the VSEPR theory. Because the core central atom, phosphorus, has three P-Cl bonds with the surrounding three chlorine atoms in the bottom of tetrahedral geometry. In the same plane, the Cl-P-Cl bond forms a 109-degree angle. Because three chlorine atoms are in the same plane, they form a tetrahedral pyramidal or trigonal pyramidal shape.
Above that top of tetrahedral geometry, there is one lone pair. It maintains the tetrahedral-like form after connecting the upper one lone pairs to the trigonal pyramidal form. The lone pair is located just top to bond pairs in the tetrahedral geometry. The one lone pair of the electron is just above the trigonal pyramidal bond pair plane in the tetrahedral geometry.
Because of the one lone pair of electrons, it gives tetrahedral electron geometry. But the PCl3 molecular geometry is a trigonal pyramidal structural form in nature. It is the asymmetrical geometry of the PCl3 molecule. That makes, PCl3 molecule is polar.
How to find PCl3 molecular geometry
In the case of PCl3, the center atom, phosphorus, has five outermost valence shell electrons and three chlorine atoms connected to it.
As a result of this, L.P(P) = (5 – 3)/2=1
The lone pair on the center phosphorus atom of the PCl3 electron geometry structure is equal to one. It means, the central phosphorus atom contains one lone pair.
Phosphorus, then, is a central atom with three chlorine atoms linked to it and one lone pair in the PCl3 molecule. Then the number of hybridization (No. Hyb) can be calculated as follows
No. Hyb = 3+1 =4
Number of hybridization for PCl3 molecule is four. one S orbital, and three p orbitals combine together to form the sp3 hybridization.
3. Use VSEPR theory to determine PCl3 molecular geometry shape
When the VSEPR theory is utilized to calculate the shape of the PCl3 molecule, the AXN approach is typically used.
We know phosphorus is the center atom with three bound (P-Cl) pairs of electrons and one lone pair. because of the PCl3 Lewis structure. PCl3 has the general molecular geometry formula AX3N1.
If the molecule has an AX3N1 generic formula, the molecular geometry will be trigonal pyramidal and the electron geometry will be tetrahedral, according to the VSEPR theory.
|Name of Molecule||Phosphorus trichloride|
|Chemical molecular formula||PCl3|
|Molecular geometry of PCl3||Trigonal pyramidal|
|Electron geometry of PCl3||Tetrahedral|
|Hybridization of PCl3||Sp³|
|Bond angle (Cl-P-Cl)||109º degree|
|Total Valence electron for PCl3||26|
|The formal charge of PCl3 on Phosphorus||0|
Why is PCl3 polar?
Is PCl3 ionic or polar?
Is PCl3 nonpolar covalent?
Is PCl3 dipole dipole?