Structure, Molecular Geometry, and Hybridization of PH3 Lewis

Phosphorous Trihydride (PH3), sometimes referred to as phosphine, is composed of phosphorous and hydrogen atoms. It is a colourless, poisonous, and combustible gas.

Pure phosphine has no odour, yet the majority of phosphine samples smell like rotting garlic or decomposing fish.

This compound is employed as a pesticide and for cereal fumigation. This substance is also utilised in the semiconductor and plastics industries.

Phosphene has a chemical formula of PH3, which indicates that it has one phosphorous and three hydrogen atoms.

This compound’s molecular structure, shape, and hybridization will be fascinating to examine.

Lewis Structure of Phosphene

The chemical formula of phosphene is PH3, indicating that one phosphorous atom is bonded to three hydrogen atoms.

To comprehend the structure of PH3, we must know the electronic configuration of the atoms and the number of valence electrons.

Hydrogen’s electrical configuration is 1S1 because it has only one electron.

The electrical configuration of phosphorus is 1S2 2S2 2P6 3S2 3P3.

Hydrogen is located in the first column of the periodic table, whereas phosphorus is in the fifth column.

This indicates that hydrogen has one valence electron and phosphorus has three. Three hydrogen atoms interact with phosphorus to form phosphene.

The electrical arrangement of the atoms reveals the number of atoms that can form bonds.

Since hydrogen has one valence electron and phosphorus has three, P is the core atom in this compound’s molecular structure.

Three phosphorous valence electrons combine with three hydrogen valence electrons to make three pairs. Phosphorous’s remaining two unpaired electrons are placed on the fourth side, forming a lone pair.

Checking the surrounding electrons of both compounds reveals that each Hydrogen atom is surrounded by two electrons, whereas the phosphorous atom is surrounded by eight electrons.

Consequently, the combination now has a stable structure.

PH3 has a bond angle of 93 degrees. This compound’s geometric structure has the shape of a trigonal pyramid. In the following section, we will examine the geometric geometry of this combination in greater depth.

The Molecular Structure of Phosphene

Two elements govern the molecular geometry of a compound: the Lewis structure and the VSEPR (valence shell electron pair repulsion) theory.

According to the Lewis structure of PH3, the phosphorous atom contains five valence electrons.

Phosphorous is surrounded by three hydrogen atoms, each of which is joined by a single connection during the bonding process.

The remaining two electrons constitute a lone pair. The amount of lone pairs and the number of covalent bonds within a molecule define its form.

If you have studied the VSEPR theory, you are aware that each pair of electrons tends to maintain the greatest feasible separation.

It decreases the repulsion between the valence electrons, hence aiding in the formation of a stable molecular structure. A molecule’s form is determined by the quantity of lone pairs and bonds.

Every pair of electrons repels every other pair; the force of repulsion is greatest between two lone pairs.

This force is weakest between two electron bond pairs.

Here is an ascending list of repelling forces:

Bond pair – bond pair < bond pair – lone pair < lone pair – lone pair

There is one lone pair and three bond pairs in the PH3 molecule. Therefore, the lone pair maintains the greatest distance possible from the three bond pairs.

As a result, the PH3 molecule assumes the shape of a trigonal pyramid, with the three bond pairs forming the pyramid’s base and the lone pair remaining at the top, maintaining a greater distance from the other three bond pairs.

This shape (trigonal pyramid) is due to the three electron pairs and the stronger repulsive force between the lone pair and the three bond pairs.

The PH3 Molecule’s Hybridization

What exactly is hybridization?

Orbital hybridization is the concept of merging two or more atomic orbitals with the same energy level to generate a new type of orbitals.

Using carbon as an example, atoms create bonds by mixing their s and p orbitals. Carbon creates a variety of chemicals through hybridization.

Understanding how the atoms are placed within a molecule improves comprehension of the molecule’s shape.

To comprehend the various chemical components around us, it is vital to grasp and visualise the three-dimensional structure of molecules.

It improves your grasp of a substance’s structure, physical and chemical qualities.

Purpose of Hybridization

When an atom participates in a chemical bond by sharing electrons from its s and p orbitals, hybridization occurs.

During this type of chemical interaction, an imbalance in the energy levels is generated, and in order to rectify this imbalance, the orbitals mix, producing a hybrid orbital.

Since you now have a clear understanding of hybridization, it will be simpler to comprehend the hybridization of PH3.

Combination of PH3

It is rather unexpected that Phosphine does not undergo hybridization. This is due to the compound’s unusual orbital structure and electron distribution.

Examine why this occurs with the phosphene molecule.

Analyzing the structure of the PH3 molecule reveals that the valence electrons in the p orbitals contribute to bond formation. It prevents hybridization of the p orbital.

Phosphorous has one lone pair and three bond pairs in PH3. The Drago rule better explains the hybridization of PH3. In the following part, we shall examine Drago’s rule in the phosphine hybridization process.

Drago’s Rule and Phosphine Hybridization

Under some conditions, hybridization in a molecule will not occur according to Drago’s rule. The conditions are as follows.

Or less than 2.5, the electronegativity of the centre element.

The sum of the number of lone pairs and sigma bonds is four.

The centre atom is assigned to one of the groups between 13 and 17 or the Period 3 to 7.

At least one lone pair exists in the centre atom.

Phosphorous is the atom at the centre of the phosphine molecule. According to the current periodic table, it belongs to the third period and fifteenth group.

2.9 is the electronegativity of phosphorus. Moreover, phosphine has a single pair.

Therefore, it satisfies three conditions of Drago’s rule, and we know that hybridization does not occur when a compound satisfies only one of Drago’s rules.

Consequently, hybridization does not occur in the PH3 molecule.

Polarization in PH3

Ph3 is considered a polar molecule due to the presence of a lone pair, which gives the molecule its trigonal pyramidal shape.

As a result, the charge distribution over the entire molecule is not uniform.

Additionally, you must read the article on the polarity of PH3 for more information.

Facts Regarding Phosphine

There is no orbital hybridization in PH3 molecules.

The pure ‘p’ orbitals in the PH3 molecule contribute to the creation of the P-H bond.

Ph3 has a bond angle of 93.5 degrees.


This page provides a summary of the phosphene (PH3) molecule’s Lewis structure, molecular geometry, and hybridization.

We have attempted to address every aspect of this topic, including Drago’s rule, which explains why this chemical lacks hybridization.

In addition to this, you have acquired some intriguing information about this chemical. I sincerely hope you enjoyed reading it.

Read more: Polar or nonpolar is SCl2?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


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