PH3 Molecular Geometry - Science Education and Tutorials

Q: What is the molecular notation for PH3 molecule?

PH3 molecular notation is AX3N1.

Drawing and predicting the PH3 molecular geometry is very easy by following the given method. Here in this post, we described step by step to construct PH3 molecular geometry.

Table of Contents

Key Points To Consider When drawing The PH3 Molecular Geometry

A three-step approach for drawing the PH3 molecular can be used. The first step is to sketch the molecular geometry of the PH3 molecule, to calculate the lone pairs of the electron in the central Phosphorous atom; the second step is to calculate the PH3 hybridization, and the third step is to give perfect notation for the PH3 molecular geometry.

The PH3 molecular geometry is a diagram that illustrates the number of valence electrons and bond electron pairs in the PH3 molecule in a specific geometric manner. The geometry of the PH3 molecule can then be predicted using the Valence Shell Electron Pair Repulsion Theory (VSEPR Theory) and molecular hybridization theory, which states that molecules will choose the PH3 geometrical shape in which the electrons have from one another in the specific molecular structure.

Finally, you must add their bond polarities characteristics to compute the strength of the P-H bond (dipole moment properties of the PH3 molecular geometry). The Phosphorous-hydrogen bonds in the Phosphine molecule(PH3), for example, are polarised toward the more electronegative value Phosphorous atom, and because all (P-H) bonds have the same size and polarity, their sum is non zero due to the PH3 molecule’s bond dipole moment, and the PH3 molecule is classified as a polar molecule.

The molecule of Phosphine (with tetrahedral shape PH3 molecular geometry) is tilted at 107 degrees. It has a difference in electronegativity values between Phosphorous and hydrogen atoms, with Phosphorous’s pull the electron cloud being greater than hydrogen’s. As a result, it has a permanent dipole moment in its molecular structure. The PH3 molecule has a dipole moment due to an unequal charge distribution of negative and positive charges.

Overview: PH3 electron and molecular geometry

According to the VSEPR theory, PH3 possesses tetrahedral molecular geometry and CH4-like electron geometry. Because the center atom, Phosphorous, has three P-H bonds with the hydrogen atoms surrounding it. The H-P-H bond angle is 107 degrees in the tetrahedral molecular geometry. The PH3 molecule has a tetrahedral geometry shape because it contains three hydrogen atoms.

There are three P-H bonds at the PH3 molecular geometry. After linking the three hydrogens and one lone pair of electrons in the tetrahedral form, it maintains the tetrahedral-like structure. In the PH3 molecular geometry, the P-H bonds have stayed in the three terminals and lone pair of electrons in the top of the tetrahedral molecule.

The center Phosphorous atom of PH3 has one lone pair of electrons, resulting in tetrahedral electron geometry. However, the molecular geometry of PH3 looks like a tetrahedral and one lone pair on the top of the geometry. It’s the PH3 molecule’s asymmetrical geometry. As a result, the PH3 molecule is polar.

How to find PH3 hybridization and molecular geometry

Calculating lone pairs of electrons on Phosphorous in the PH3 molecular geometry:

1.Determine the number of lone pairs on the core Phosphorous atom of the PH3 Lewis structure. Because the lone pairs on Phosphorous are mostly responsible for the PH3 molecule geometry distortion, we need to calculate out how many there are on the central Phosphorous atom of the Lewis structure.

Use the formula below to find the lone pair on the Phosphorous atom of the PH3 molecule.
L.P(P) = V.E(P) – N.A(P-H)/2

Lone pair on the central Phosphorous atom = L.P(P)
The core central Phosphorous atom’s valence electron = V.E(P)
Number of P-H bonds = N.A (P-H )
calculation for Phosphorous atom lone pair in PH3 molecule

For instance of PH3, the central atom, Phosphorous, has five electrons in its outermost valence shell, three P-H bond connections.

As a result of this, L.P(P) = (5 –3)/2=1

In the PH3 electron geometry structure, the lone pair on the central Phosphorous atom is one. It means there is one lone pair in the core Phosphorousn atom. These lone pair on the central Phosphorous atom is responsible for the PH3 molecular geometry distortion.

If you imagine, there is one lone pair on the Phosphorous atom of the PH3 molecule. Then, electronic repulsion of P-H bonds pair and one lone pair of electrons in the PH3. That gives stable tetrahedral geometry.

But in reality, the PH3 molecule undergoes distortion in its geometry due to the polarity of the P-H bond and lone pairs of electrons in the tetrahedral geometry. This leads to tetrahedral geometry for the PH3 molecule.

Calculate the number of molecular hybridizations of PH3 molecule

What is PH3 hybridization? This is a very fundamental question in the field of molecular chemistry. All the molecules are made by atoms. In chemistry, atoms are the fundamental particles. There are four different types of orbitals in chemistry. They are named s, p, d, and f orbitals.

The entire periodic table arrangement are based on these orbital theory. Atoms in the periodic table are classified as follows:

s- block elements
p- block elements
d-block elements
f-block elements
Atoms are classified in the periodic table

PH3 molecule is made of one Phosphorous and three hydrogens atoms. The Phosphorous atom has s and p orbital. hydrogen comes as the first element in the periodic table. The hydrogen atom has s orbital.

When these atoms combine to form the PH3 molecule, its orbitals mixed and form unique molecular orbitals due to hybridization.

How do you find the PH3 molecule’s hybridization? We must now determine the molecular hybridization number of PH3.

The formula of PH3 molecular hybridization is as follows:
No. Hyb of PH3= N.A(P-H bonds) + L.P(P)
No. Hy of PH3= the number of hybridizations of PH3
Number of P-H bonds = N.A (P-H bonds)
Lone pair on the central Phosphorous atom = L.P(P)
Calculation for hybridization number for PH3 molecule

In the PH3 molecule, Phosphorous is a core atom with three hydrogen atoms connected to it and one lone pair of electrons. The number of PH3 hybridizations (No. Hyb of PH3) can then be estimated using the formula below.

No. Hyb of PH3= 3+1 =4

The PH3 molecule hybridization is four. The sp3 hybridization of the PH3 molecule is formed when one S orbital and three p orbital join together to form a molecular orbital.

Molecular Geometry Notation for PH3 Molecule :

Determine the form of PH3 molecular geometry using VSEPR theory. The AXN technique is commonly used when the VSEPR theory is used to calculate the shape of the PH3 molecule.

The AXN notation of PH3 molecule is as follows:
The center Phosphorous atom in the PH3 molecule is denoted by the letter A.
The bound pairs (three P-H bonds) of electrons to the core Phosphorous atom are represented by X.
The lone pairs of electrons on the center Phosphorous atom are denoted by the letter N.
Notation for PH3 molecular geometry

We know that Phosphorous is the core atom, with three electron pairs bound (three P-H) and one lone pair of electrons. The general molecular geometry formula for PH3 is AX3N1.

According to the VSEPR theory, if the PH3 molecule has an AX3N1 generic formula, the molecular geometry and electron geometry will both be tetrahedral forms.

Name of Molecule	Phosphine
Chemical molecular formula	PH3
Molecular geometry of PH3	Tetrahedral
Electron geometry of PH3	Tetrahedral
Hybridization of PH3	sp3
Bond angle (H-P-H)	107º degree
Total Valence electron for PH3	8
The formal charge of PH3 on Phosphorous	0

Summary:

In this post, we discussed the method to construct PH3 molecular geometry, the method to find the lone pairs of electrons in the central Phosphorous atom, PH3 hybridization, and PH3 molecular notation. Need to remember that, if you follow the above-said method, you can construct the PH3 molecular structure very easily.