How to draw PF3 Lewis Structure? - Science Education and Tutorials

Q: What is the PF3 Lewis structure?

PF3 Lewis structure is dot representation

Q: What is the formal charge on the PF3 Lewis structure?

Zero charges on the PF3 molecular structure

The phosphorus trifluoride chemical formula is PF3. Drawing PF3 Lewis Structure is very easy to by using the following method. Here in this post, we described step by step method to construct PF3 Lewis Structure. The phosphorus and fluorine elements come as the member of the nitrogen and halogen family groups from the periodic table respectively. The valence electrons in phosphorus and fluorine are five and seven respectively. The branch of phosphorus halogen compound chemistry is used to make chemicals reagents for organic chemical reactions.

Table of Contents

Key Points To Consider When Drawing The PF3 Electron Dot Structure

A three-step approach for drawing the PF3 Lewis structure can be used. The first step is to sketch the Lewis structure of the PF3 molecule, to add valence electrons around the phosphorus atom; the second step is to add valence electrons to the three fluorine atoms, and the final step is to combine the step1 and step2 to get the PF3 Lewis Structure.

The PF3 Lewis structure is a diagram that illustrates the number of valence electrons and bond electron pairs in the PF3 molecule. The geometry of the PF3 molecule can then be predicted using the Valence Shell Electron Pair Repulsion Theory (VSEPR Theory), which states that molecules will choose the PF3 geometrical shape in which the electrons have from one another.

Finally, you must add their bond polarities to compute the strength of the three P-F single bonds (dipole moment properties of the PF3 molecule). The phosphorus-fluorine bonds in phosphorus trifluoride(PF3), for example, are polarised toward the more electronegative fluorine in PF3 molecule, and because both bonds have the same size and are located around three fluorine terminals of the trigonal pyramidal with one lone pair (in total two electrons) on the phosphorus atom, their sum of dipole moment is nonzero due to the PF3 molecule’s bond dipole moment and more electron polarity to the fluorine atoms. Because each three P-F bonds polarity not canceled each other in the PF3 molecule due to the presence of one lone pair of electrons. The phosphorus trifluoride(PF3) molecule is classified as a polar molecule.

The molecule of phosphorus trifluoride (with trigonal pyramidal molecular geometry) is tilted, the bond angles between phosphorus and fluorine are 97 degrees. It has a difference in electronegativity values between phosphorus and fluorine atoms, with central phosphorus’s pull being less than terminal fluorine’s in the PF3 molecule. But they not canceled each other due to the asymmetrical trigonal pyramidal with one lone pair in the molecular geometry of the PF3 molecule.

As a result, it has the nonzero dipole moment. The PF3 molecule has a nonzero dipole moment due to an unequal charge distribution of negative and positive charges. But both phosphorus and fluorine atoms fall on the nitrogen and halogen family groups in the periodic table respectively. The fluorine atom is a more electronegative value than phosphorus in the PF3 molecule. The PF3 molecule has the net dipole moment of 1.03D value in the ground state energy state.

PF3 molecule has three P-F single bonds. Its dipole moment in the ground state is totally different as compared with the excited state. If it absorbs light may be from visible or UV light. It undergoes pi to pi star and n to pi star transition from ground state energy level to excited state energy level. In the excited state energy level, the PF3 molecule shows a definite dipole moment. But it is very dynamics.

Molecules can be classified as polar or nonpolar. The molecule polar behaves in a different manner as compared to nonpolar.

Overview: PF3 Lewis Structure

The central atom is phosphorus, which is bordered on three terminals with fluorine atoms( in trigonal pyramidal geometry), and one lone pair on the central phosphorus atom in the trigonal pyramidal molecular geometry. Phosphorus has five outermost valence electrons, indicating that it possesses five electrons in its outermost shell, whereas fluorine also has seven valence electrons in its outermost shell. To complete the octet of the phosphorus and fluorine atoms requires three and one valence electrons on each of their outermost shell respectively.

Three fluorine atoms establish covalent connections with the central phosphorus atom as a result, leaving the phosphorus atom with one lone pair. There is one lone pair of electrons on the phosphorus central atom that resists the bond pairs of the three P-F bonds. According to VSEPR theory, the single P-F bond pairs polarity lead the PF3 molecule to take on the trigonal pyramidal geometry structure.

The PF3 molecule’s three P-F bonds are arranged in symmetrical polarity order around the trigonal pyramidal molecular geometry, giving rise to the PF3 molecular shape. The PF3 molecule has a trigonal pyramidal molecular geometry because there is an electrical repulsion between the lone pairs of electrons in phosphorus and three single bond pairs(P-F) of the PF3 molecule.

Lewis structure of PF3 has dot electron representative structure. Valence electrons of atoms undergo orbitals mixing in the chemical reactions, gives new types of molecular species of PF3. The molecule is nothing but a bundle of valence electrons from the atoms. But it is converted to bond pairs and lone pairs in the molecular structure.

Electronegative value Difference Calculation of PF3 Molecule:

Phosphorus and fluorine Electronegative difference in PF3:

The phosphorus atom has an electronegativity of 2.19, while fluorine has an electronegativity of 3.98 in the PF3 molecule. The difference in electronegativity of phosphorus and fluorine can be estimated using the method below.

The electronegative value difference between phosphorus and fluorine in PF3 molecule
Electronegativity value of phosphorus = 2.19
Electronegativity value of fluorine= 3.98
Difference of electronegativity value between phosphorus and fluorine in PF3 molecule = 3.98 – 2.19 = 1.79
Electronegativity difference between P-F bond calculation of PF3 molecule

The electronegative difference between phosphorus and fluorine is greater than 0.5. This indicated the bond polarity moves near to polar nature. P-F bond polarity in the PF3 molecule is polar.

Because of this difference in electronegativity of phosphorus and fluorine atoms, the PF3 molecule’s P-F bond becomes polar. The total net dipole moment of the PF3 molecule is nonzero due to the noncancellation of the bond dipole moment in the trigonal pyramidal geometry. The electronegativity of an atom is the strength with which it may attract bound electron pairs to its side. The polarity of PF3 is discussed in our previous post.

As a result, the P-F bond’s dipole moment is high due to the polarization of the bonds and one lone pair of electrons on phosphorus, and all P-F bonds’ dipoles are arranged in the asymmetrical PF3 molecular geometry. The PF3 molecule has a nonzero net dipole moment.

The electron dot structure of the PF3 molecule is also known as the PF3 Lewis structure. It determines the number of outermost valence electrons as well as the electrons engaged in the PF3 molecule’s bond formation. The outermost valence electrons of the PF3 molecule must be understood while considering the Lewis structure of the molecule.

The phosphorus atom is the middle element in PF3 molecular geometry, with five electrons in its outermost valence electron shell, whereas the fluorine atom has seven electrons in its outermost valence electron shell. The fluorine atom has seven valence electrons.

The PF3 has a total of 26 valence electrons as a result of the foregoing above-said reasoning. With the core central phosphorus atom, the three terminals with three fluorine atoms form covalent bonds, leaving the phosphorus atom with one lone pair in the middle of trigonal pyramidal geometry.

Because lone pairs on the terminal fluorine atoms create interaction with P-F bond pairs(but it is negligible in the ground state of the PF3 molecule). The bond angle of the F-P-F bond in the trigonal pyramidal molecular geometry is approximately 97 degrees. This angle is less than the CH4 molecule bond angle. The P-F bond length is 142pm(picometer).

To sketch the PF3 Lewis structure by following these instructions:

Step-1: PF3 Lewis dot Structure by counting valence electrons on the phosphorus atom

To calculate the valence electron of each atom in PF3, look for its periodic group from the periodic table. The nitrogen and halogen group families, which are the 15th and 17th groups in the periodic table, are both made up of phosphorus and fluorine atoms respectively. In their outermost shells, fluorine and phosphorus have seven and five valence electrons respectively.

Calculate the total number of valence electrons in the PF3 molecule’s outermost valence shell. The first step is to determine how many electrons are in the PF3 Lewis structure’s outermost valence shell. An electron in an atom’s outermost shell is known as a valence electron. It is represented by dots in the PF3 Lewis diagram. The PF3 molecule’s core phosphorus atom can be represented as follows:

Total outermost valence shell electron of phosphorus atom in PF3= 5
Total outermost valence shell electron of fluorine atom in PF3= 7
The PF3 molecule has one central phosphorus and three fluorine atoms. Then the total outermost valence shell electrons can be calculated as follows
∴ Total outermost valence shell electrons available for PF3 Lewis structure( dot structure) = 5+3*7= 26 valence electrons in PF3.
calculation of total valence electron of PF3 molecule

Choose the atom with the least electronegative value atom and insert it in the center of the molecular geometry of PF3. We’ll choose the least electronegative value atom in the PF3 molecule to place in the center of the PF3 Lewis structure diagram in this phase. The electronegativity value in periodic groups grows from left to right in the periodic table and drops from top to bottom.

The first step is to put five valence electrons around the phosphorus atom as given in the figure.

Step-2: Lewis Structure of PF3 for counting valence electrons around the terminal fluorine atoms

As a result, phosphorus is the first atom in the periodic table’s nitrogen family group. Fluorine is the first member of the halogen family. The electronegative value of the fluorine atom is higher than that of the phosphorus atom in the PF3 molecule. Furthermore, fluorine has a seven electrons limit since phosphorus is the less electronegative element in the PF3 molecule.

In the PF3 Lewis structure diagram, the phosphorus atom can be the center atom of the molecule. As a result, central phosphorus in the PF3 Lewis structure, with all three fluorine atoms arranged in a trigonal pyramidal geometry.

Add valence electrons around the fluorine atom, as given in the figure.

Step-3: Lewis dot Structure for PF3 generated from step-1 and step-2

Connect the exterior and core central atom of the PF3 molecule with three single P-F bonds. In this stage, use three fluorine atoms on the outside of the PF3 molecule to the central phosphorus atom in the middle.

Count how many electrons from the outermost valence shell have been used in the PF3 structure so far. Each P-F single bond carries two electrons because each phosphorus atom is connected to three fluorine atoms by three P-F single bonds. Bond pairings of P-F are what they’re called.

So, out of the total of 26 valence electrons available for the PF3 Lewis structure, we used six electrons for the PF3 molecule’s three P-F single bonds. The PF3 molecule has one lone pair of electrons in the central phosphorus atom.

Place the valence electrons in the P-F bond pairs starting with the core phosphorus, three fluorine atoms in the PF3 molecule. In the PF3 Lewis structure diagram, we always begin by introducing valence electrons from the central phosphorus atom(in step1). As a result, wrap around the central phosphorus atom’s bond pair valence electrons first (see figure for step1).

The phosphorus atom in the molecule gets only 8 electrons around its molecular structure. This central phosphorus atom is octet stable. But it has one lone pair. Phosphorus is a brownish solid in nature. Phosphorus catch fire in the exposure to air. But phosphorus is used in matchboxes and firecrackers.

Fluorine(F2) is in the gaseous state at normal temperature and pressure. It is used as a fluorinating agent in the field of organic chemistry. It is a highly corrosive gas. It is responsible for dry corrosion in the metal bodies. It is very reactive to bio-micro organisms.

Phosphorus requires 8 electrons in its outermost valence shell to complete the molecular octet stability, six electrons bond pairs in three P-F single bonds, and one lone pair in the central phosphorus atom. Then lone pair of electrons on the fluorine atoms of the PF3 molecule is placed in a trigonal pyramidal geometry. Phosphorus already shares 8 electrons to the three P-F single bonds. Then place the valence electron in the fluorine atoms, it placed around seven electrons on each atom(step-2). 18 valence electrons were placed around three fluorine atoms as lone pairs of electrons.

We’ve positioned 18 electrons around the three-terminal fluorine atoms(step-3), which is represented by a dot, in the PF3 molecular structure above. The phosphorus atom completes its molecular octet stability in the PF3 molecule because it possesses six electrons in its (three P-F single bonds) bond pairs with three fluorine in the outermost valence shell.

Count how many outermost valence shell electrons have been used so far using the PF3 Lewis structure. three electron bond pairs are shown as dots in the PF3 chemical structure, whereas three single bonds each contain two electrons. The outermost valence shell electrons of the PF3 molecule(bond pairs) are six as a result of the calculation. The total valence electron in a phosphorus atom is 8.

So far, we’ve used 26 of the PF3 Lewis structure’s total 26 outermost valence shell electrons. One lone pair of electrons on the phosphorus atom in the trigonal pyramidal geometry of the PF3 molecule.

Complete the middle phosphorus atom stability and, if necessary, apply a covalent bond. The central phosphorus atom undergoes octet stability(due to three single bond pairs of electrons).

The core atom in the PF3 Lewis structure is phosphorus, which is bonded to the three fluorine atoms by single bonds (three P-F). With the help of three single bonds, it already shares 8 electrons. As a result, the phosphorus follows the octet rule and has 8 electrons surrounding it on the three terminals of the PF3 molecule’s trigonal pyramidal geometry.

How to calculate the formal charge on phosphorus and fluorine atoms in PF3 Lewis Structure?

Calculating formal charge on the phosphorus of PF3 molecule:

The formal charge on the PF3 molecule’s phosphorus central atom often corresponds to the actual charge on that phosphorus central atom. In the following computation, the formal charge will be calculated on the central phosphorus atom of the PF3 Lewis dot structure.

To calculate the formal charge on the central phosphorus atom of the PF3 molecule by using the following formula:
The formal charge on the phosphorus atom of PF3 molecule= (V. E(P)– L.E(P) – 1/2(B.E))
V.E (P) = Valence electron in a phosphorus atom of PF3 molecule
L.E(P) = Lone pairs of an electron in the phosphorus atom of the PF3 molecule.
B.E = Bond pair electron in P atom of PF3 molecule
calculation of formal charge on phosphorus atom in PF3 molecule

The phosphorus core atom (three single bonds connected to three fluorine atoms ) of the PF3 molecule has five valence electrons, one lone pair of electrons(two electrons), and six bonding pairing valence electrons. Put these values for the phosphorus atom in the formula above.

Formal charge on phosphorus atom of PF3 molecule = (5- 2-(6/2)) =0

In the Lewis structure of PF3, the formal charge on the central phosphorus atom is zero.

Calculating formal charge on the fluorine atom of PF3 molecule:

The formal charge on the PF3 molecule’s fluorine terminal atoms often corresponds to the actual charge on that fluorine terminal atoms. In the following computation, the formal charge will be calculated on the terminal fluorine atom of the PF3 Lewis dot structure.

To calculate the formal charge on the terminal fluorine atom of the PF3 molecule by using the following formula:
The formal charge on the fluorine atom of PF3 molecule= (V. E(F)– L.E(F) – 1/2(B.E))
V.E (F) = Valence electron in a fluorine atom of PF3 molecule
L.E(F) = Lone pairs of an electron in the fluorine atom of the PF3 molecule.
B.E = Bond pair electron in F atom of PF3 molecule
calculation of formal charge on fluorine atom in PF3 molecule

The fluorine terminal atoms of the PF3 molecule have seven valence electrons, three lone pairs of electrons(six electrons), and two bonding pairing valence electrons(single bond). Put these values for the fluorine atom in the formula above.

Formal charge on fluorine atom of PF3 molecule = (7- 6-(2/2)) =0

In the Lewis structure of PF3, the formal charge on the terminal fluorine atom is zero.

Summary:

In this post, we discussed the method to construct the PF3 Lewis structure. First, the valence electrons are placed around the phosphorus atom. Second, place the valence electron on the fluorine atoms. Finally, when we combined the first and second steps. It gives PF3 Lewis structure. Need to remember that, if you follow the above-said method, you can construct molecular dot structure very easily.