PF3 Molecular Geometry - Science Education and Tutorials

Q: What is the molecular notation for PF3 molecule?

PF3 molecular notation is AX3N1.

Phosphorus trifluoride(PF3) has the composition of one phosphorus and three fluorine atoms. What is the molecular geometry of phosphorus trifluoride?. Drawing and predicting the PF3 molecular geometry is very easy by following the given method. Here in this post, we described step by step to construct PF3 molecular geometry. Phosphorus and fluorine come from the 15th and 17th family groups in the periodic table. Phosphorus and fluorine have five and seven valence electrons respectively.

Table of Contents

Key Points To Consider When drawing The PF3 Molecular Geometry

A three-step approach for drawing the PF3 molecular can be used. The first step is to sketch the molecular geometry of the PF3 molecule, to calculate the lone pairs of the electron in the central phosphorus atom; the second step is to calculate the PF3 hybridization, and the third step is to give perfect notation for the PF3 molecular geometry.

The PF3 molecular geometry is a diagram that illustrates the number of valence electrons and bond electron pairs in the PF3 molecule in a specific geometric manner. The geometry of the PF3 molecule ion 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 PF3 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 three P-F single bonds (dipole moment properties of the PF3 molecular geometry). Two phosphorus-fluorine single bonds in the phosphorus trifluoride(PF3), for example, are polarised toward the more electronegative value fluorine atoms, and because all three (P-F) single bonds have the same size and polarity, their sum is nonzero due to the PF3 molecule’s bond dipole moment due to pulling the electron cloud to the three side of trigonal pyramidal geometry, and the PF3 molecule is classified as a polar molecule.

The molecule of phosphorus trifluoride(with trigonal pyramidal shape PF3 molecular geometry) is tilted at 97 degrees bond angle of F-P-F. It has a difference in electronegativity values between phosphorus and fluorine atoms, with fluorine’s pull the electron cloud being greater than phosphorus’s. But bond polarity of P-F is not canceled to each other in the trigonal pyramidal geometry. As a result, it has a nonzero permanent dipole moment in its molecular structure. The PF3 molecule has a nonzero dipole moment due to an unequal charge distribution of negative and positive charges in the trigonal pyramidal geometry.

Overview: PF3 electron and molecular geometry

According to the VSEPR theory, the PF3 molecule ion possesses trigonal pyramidal molecular geometry. Because the center atom, phosphorus, has three P-F single bonds with the three fluorine atoms surrounding it. The F-P-F bond angle is 97 degrees in the trigonal pyramidal PF3 molecular geometry. The PF3 molecule has a trigonal pyramidal geometry shape because it contains three fluorine atoms in the geometry and four corners with one lone pair of electrons.

There are three P-F single bonds at the PF3 molecular geometry. After linking the three fluorine atoms and one lone pair of electrons on the phosphorus atom in the trigonal pyramidal form, it maintains the pyramidal-shaped structure. In the PF3 molecular geometry, the P-F single bonds have stayed in the three terminals and one lone pair of electrons on the phosphorus atom of the trigonal pyramidal PF3 molecule.

The center phosphorus atom of PF3 has one lone pair of electrons, resulting in trigonal pyramidal PF3 electron geometry. However, the molecular geometry of PF3 looks trigonal pyramidal and has one lone pair of electrons on the phosphorus of the PF3 geometry. It’s the PF3 molecule’s symmetrical geometry. As a result, the PF3 molecule is polar.

How to find PF3 hybridization and molecular geometry

Calculating lone pairs of electrons on phosphorus in the PF3 geometry:

1.Determine the number of lone pairs of electrons in the core phosphorus atom of the PF3 Lewis structure. Because the lone pairs of electrons on the phosphorus atom are mostly responsible for the PF3 molecule geometry planar, we need to calculate out how many there are on the central phosphorus atom of the PF3 Lewis structure.

Use the formula below to find the lone pair on the phosphorus atom of the PF3 molecule.
L.P(P) = V.E(P) – N.A(P-F)/2

Lone pair on the central phosphorus atom in PF3 = L.P(P)
The core central phosphorus atom’s valence electron in PF3 = V.E(P)
Number of P-F bonds = N.A (P-F)
calculation for phosphorus atom lone pair in PF3 molecule.

For instance of PF3, the central atom, phosphorus, has five electrons in its outermost valence shell, three P-F single bond connections. This gives a total of three connections.

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

The lone pair of electrons in the phosphorus atom of the PF3 molecule is one.

Calculating lone pair of electrons on fluorine in the PF3 geometry:

Finding lone pair of electrons for the terminal fluorine atom is not similar to the central Phosphorus atom. We use the following formula as given below

Use the formula below to find the lone pair on the fluorine atom of the PF3 molecule.
L.P(F) = V.E(F) – N.A(P-F)

Lone pair on the terminal fluorine atom in PF3= L.P(F)
Terminal fluorine atom’s valence electron in PF3= V.E(F)
Number of P-F bonds = N.A ( P-F)
calculation for fluorine atom lone pair in PF3 molecule.

For instance of PF3, their terminal atoms, fluorine, have seven electrons in their outermost valence shell, one P-F single bond connection. This gives a total of three P-F single bond connections. But we are considering only one connection for the calculation.

As a result of this, L.P(F) = (7 –1)=6

The lone pair of electrons in the fluorine atom of the PF3 molecule is six. Three fluorine atoms are connected with the central phosphorus atom.

In the PF3 electron geometry structure, the lone pair on the central phosphorus atom is one, lone pairs of electrons in the fluorine atom have six. Three fluorine atoms have 18 lone pairs of electrons.

It means there are one lone pair of electrons in the core phosphorus atom. One lone pair of electrons on the central phosphorus atom is responsible for the trigonal pyramidal nature of PF3 molecular geometry. But in the structure fluorine atoms are polarised sidewise in their trigonal pyramidal geometry.

The one lone pair of electrons are placed at the top of the PF3 geometry. Because the Phosphorus atom is a lower electronegative value as compared with other atoms in the PF3 molecule. Three fluorine atoms are polarized towards the sidewise in the PF3 structure.

But in reality, the PF3 has one lone pair of electrons in its structure. This makes the PF3 more asymmetrical in the structure of the molecule. Because there is electric repulsion between bond pairs and lone pairs. But some sort of interaction is there between fluorine lone pairs and bond pairs. But it is negligible in the ground state.

But in the central, phosphorus atom has one lone pair of electrons and these lone pair electrons just oppose each other with phosphorus- fluorine bond pairs.

Calculate the number of molecular hybridizations of the PF3 molecule

What is PF3 hybridization? This is a very fundamental question in the field of molecular chemistry. All the molecules are made of 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 is based on these orbital theories. 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

PF3 molecule is made of one phosphorus, three fluorine atoms. The fluorine and phosphorus atoms have s and p orbitals. Fluorine comes as the first element from the halogen family in the periodic table. The phosphorus atom also belongs to the nitrogen family group. But it falls as the second element in the periodic table.

When these atoms combine to form the PF3 molecule, its atomic orbitals are mixed and form unique molecular orbitals due to hybridization.

How do you find the PF3 molecule’s hybridization? We must now determine the molecular hybridization number of PF3.

The formula of PF3 molecular hybridization is as follows:
No. Hyb of PF3= N.A(P-F bonds) + L.P(P)
No. Hy of PF3 = the number of hybridizations of PF3
Number of P-F bonds = N.A (P-F bonds)
Lone pair on the central phosphorus atom = L.P(P)
Calculation for hybridization number for PF3 molecule

In the PF3 molecule, phosphorus is a core central atom with three fluorine atoms connected to it. It has one lone pair of electrons on phosphorus. The number of PF3 hybridizations (No. Hyb of PF3) can then be estimated using the formula below.

No. Hyb of PF3= 3+1=4

The PF3 molecule ion hybridization is four. The phosphorus and fluorine atoms have s and p orbitals. The sp3 hybridization of the PF3 molecule is formed when one s orbital and three p orbitals join together to form the PF3 molecular orbital.

Molecular Geometry Notation for PF3 Molecule :

Determine the form of PF3 molecular geometry using VSEPR theory. The AXN technique is commonly used when the VSEPR theory is used to calculate the shape of the PF3 molecule.

The AXN notation of PF3 molecule is as follows:
The central phosphorus atom in the PF3 molecule is denoted by the letter A.
The bound pairs (three P-F bonds) of electrons to the core phosphorus atom are represented by X.
The lone pairs of electrons on the central phosphorus atom are denoted by the letter N.
Notation for PF3 molecular geometry

We know that phosphorus is the core atom, with two electron pairs bound (three P-F) and one lone pair of electrons. The general molecular geometry formula for PF3 is AX3N1.

According to the VSEPR theory, if the PF3 molecule ion has an AX3N1 generic formula, the molecular geometry and electron geometry will both be trigonal pyramidal forms.

Name of Molecule	Phosphorus trifluoride
Chemical molecular formula	PF3
Molecular geometry of PF3	Trigonal pyramidal
Electron geometry of PF3	Trigonal pyramidal
Hybridization of PF3	sp3
Bond angle (F-P-F)	97º degree
Total Valence electron for PF3	26
The formal charge of PF3 on phosphorus	0

Summary:

In this post, we discussed the method to construct PF3 molecular geometry, the method to find the lone pairs of electrons in the central phosphorus atom, PF3 hybridization, and PF3 molecular notation. Need to remember that, if you follow the above-said method, you can construct the PF3 molecular structure very easily.