Chlorine pentafluoride (ClF5) Lewis dot structure, molecular
geometry or shape, electron geometry, bond angle, formal
charge, hybridization
ClF5 is the chemical formula for an interhalogen compound known as penta fluoro chlorine or chlorine pentafluoride. It exists as a colorless gas with a sweet odor. It is most commonly used as an oxidizing agent, a fluorinating agent, and for pulp bleaching.
In this article, we will discuss some interesting facts about ClF5 such as how to draw its Lewis dot structure, what is its molecular geometry or shape, electron geometry, bond angle, hybridization, formal charges, etc.
So without any further delay, dive into it and start reading!
The Lewis structure of chlorine pentafluoride (ClF5) consists of a chlorine (Cl) atom at the center. It is bonded to five atoms of fluorine (F) at the sides. There are a total of 6 electron pairs around the central chlorine atom in the ClF5 Lewis dot structure. Out of these 6 electron pairs, there are 5 bond pairs and 1 lone pair of electrons.
You can easily draw the Lewis dot structure of ClF5 using the simple step-by-step guide given below.
Steps for drawing the Lewis dot structure of ClF5
1. Count the total valence electrons in ClF5
The Lewis dot structure of a molecule is referred to as a simplified representation of all the valence electrons present in it. Therefore, the very first step while drawing the Lewis structure of ClF5 is to calculate the total valence electrons present in the concerned elemental atoms.
There are 2 different elements present in ClF5 i.e., chlorine (Cl) and fluorine (F). When you search through the Periodic Table of elements, you will find that both Cl and F are halogens located in Group VII-A of the Periodic Table.
Thus, both chlorine and fluorine have a total of 7 valence electrons in each atom respectively.
∴ The ClF5 molecule consists of 1 chlorine atom and 5 atoms of fluorine. Thus, the total valence electrons available for drawing the Lewis structure of ClF5 = 7 + 5(7) = 42 valence electrons.
2. Find the least electronegative atom and place it at the center
The leastelectronegative atom is most likely to share its electrons with the atoms in its surroundings. Therefore, such an atom is placed at the center of the Lewis structure of a molecule.
Fluorine (F) is the most electronegative atom in the Periodic Table.
Thus, chlorine (Cl) is less electronegative than fluorine, and consequently, it is placed at the center of the ClF5. All the 5 F atoms are placed in their surroundings.
3. Connect outer atoms with the central atom
In this step, we join the outer F-atoms with the central chlorine atom using single straight lines, as shown in the diagram below.
Each straight line represents a single covalent bond i.e., a bond pair containing 2 electrons. There are a total of 5 single bonds in the above diagram, so the total valence electrons used out of the 42 initially available are 5(2) = 10 valence electrons.
Total valence electrons available – electrons used till step 3 = 42 – 10 = 32 valence electrons.
This means 32 valence electrons are still available to be accommodated in the Lewis dot structure of ClF5. Let’s see how we can do so.
4. Complete the octet of outer atoms
The fluorine (F) atoms are the outer atoms in the ClF5 molecule. Each F atom is bonded to the central Cl atom using single bonds. Thus, each F atom already has 2 valence electrons, and it requires 6 more valence electrons to achieve a stable octet electronic configuration.
Hence, 6 valence electrons are placed as 3 lone pairs around each F atom in the Lewis structure of ClF5 as shown below.
5. Place the remaining electrons as lone pairs on the central atom
Total valence electrons used till step 4 = 5 single bonds + 5 (electrons placed around each F-atom, shown as dots) = 5(2) + 5(6) = 40 valence electrons.
Total valence electrons available – electrons used till step 4 = 42 – 40 = 2 valence electrons.
Thus, these 2 electrons are placed as a lone pair on the central chlorine atom in the ClF5.
In this way, the central chlorine (Cl) atom has a total of 12 valence electrons in the ClF5 Lewis structure. This means it has an expanded octet. It is due to the availability of the 3d subshell in the chlorine atom that it can accommodate more than 8 electrons in its valence shell during chemical bonding. After completely filling the 3p atomic orbital, electrons start filling d orbitals.
As a final step, we need to check the stability of this Lewis structure. Let’s do that using the formal charge concept.
6. Check the stability of the ClF5 Lewis structure using the formal charge concept
The less the formal charge on the atoms of a molecule, the better the stability of its Lewis structure.
The formal charge can be calculated using the formula given below.
What are the electron and molecular geometry of ClF5?
The ideal electronic geometry of a chlorine pentafluoride (ClF5) molecule is octahedral. However, the presence of a lone pair of electrons on the central Cl-atom leads to lone pair-bond pair electronic repulsions.
This strong repulsive effect distorts the shape and geometry of the molecule. Consequently, ClF5 occupies a square pyramidal shape or molecular geometry.
Molecular geometry of ClF5
The molecular geometry or shape of the ClF5 molecule is square pyramidal. A lone pair of electrons present on the central chlorine atom in ClF5 leads to strong lone pair-bond pair repulsions in addition to Cl-F bond pair-bond pair electronic repulsions.
Lone pair-bond pair repulsions are stronger than bond pair-bond pair repulsions which results in distortion in the overall shape and geometry of the molecule.
Four F-atoms lie at the four corners of the square base, pushed away from the center of the molecule. Conversely, the fifth F atom and a lone pair occupy equatorial positions. Thus, a pyramid is formed at the top of the square base, as shown in the figure below.
Electron geometry of ClF5
According to the VSEPR concept, the ClF5 molecule has an octahedral electron geometry as there are a total of 6 electron density regions around the central Cl atom in the ClF5 molecule.
One should keep in mind that the ideal electron geometry is based on the total electron density regions around the central atom in a molecule. Each electron pair whether it’s a bond pair or a lone pair is considered one region of electron density.
A quick and more straightforward way of finding the electron and molecular geometry or shape of a molecule such as ClF5 is using the AXN method.
AXN is a simple formula to represent the number of atoms bonded to the central atom in a molecule and the number of lone pairs present on it.
It is used to predict the geometry or shape of a molecule using the VSEPR concept.
AXN notation for ClF5 molecule
A in the AXN formula represents the atom present at the center of a molecule. In ClF5, chlorine (Cl) is present at the center so A = Cl.
X denotes the number of atoms directly bonded to the central atom. In ClF5, 5 fluorine (F) atoms are bonded to central Cl. Thus X=5.
N stands for the number of lone pairs present on the central atom. In ClF5, 1 lone pair is present on the central Cl. Hence N=1.
This shows that the AXN generic formula for the ClF5 molecule is AX5N1.
Now use the VSEPR chart given below to identify the electron and molecular geometry, or shape assigned next to AX5N1.
The VSEPR chart indicates that molecules with AX5N1 generic formula have a square pyramidal shape or molecular geometry while their ideal electron geometry is octahedral, as we already noted down for the ClF5 molecule.
Hybridization of ClF5
The central chlorine (Cl) atom is sp3d2 hybridized in the ClF5 molecule.
The electronic configuration of chlorine is 1s2 2s2 2p6 3s2 3p5.
During chemical bonding, two 3p electrons of chlorine get excited and shift to two separate empty 3d atomic orbitals. The 3s, three 3p, and two 3d atomic orbitals of chlorine hybridize to yield six sp3d2 hybrid orbitals.
One of these six hybrid orbitals contains paired electrons. These paired electrons are situated as lone pairs on the central Cl atom in ClF5.
The remaining five sp3d2 hybrid orbitals contain a single electron each which they use for sigma (σ) bond formation with the p orbitals of fluorine atoms in ClF5, one on each side of the molecule, as shown below.
A short trick for finding the hybridization present in a molecule is to memorize the table given below. You can calculate the steric number of a molecule and use that against this table to determine its hybridization.
The steric number of central Cl in ClF5 is 6 so it has sp3d2 hybridization.
Steric number
Hybridization
2
sp
3
sp2
4
sp3
5
sp3d
6
sp3d2
The ClF5 bond angle
The F-Cl-F bond angle in the ClF5 molecule is 90° due to the square base. The Cl-F bond lengths lie between 162-175 pm.
Chlorine pentafluoride (ClF5) is a polar molecule. Fluorine (F) is highly electronegative in nature. An electronegativity difference of 0.82 units exists between the bonded fluorine (E.N = 3.98) and chlorine (E.N = 3.16) atoms in each Cl-F bond.
Thus, all the 5 Cl-F bonds present in the ClF5 molecule are polar and possess a specific dipole moment value (symbol μ).
The dipole moments do not get canceled in the molecule overall due to its asymmetric shape. The electron cloud stays non-uniformly distributed throughout thus ClF5 is polar (net μ = 1.8 Debye).
The Lewis dot structure of chlorine pentafluoride (ClF5) displays a total of 42 valence electrons i.e., 42/2 = 21 electron pairs.
Out of the 21 electron pairs, there are 5 bond pairs and 16 lone pairs of electrons.
3 lone pairs of electrons are present on each of the outer F-atoms while 1 lone pair is present on the central Cl-atom in the ClF5 Lewis structure as shown below.
What is the shape of ClF5 using VSEPR theory?
ClF5 has an AX5N1 generic formula according to the VSEPR theory. There are 5 F-atoms bonded to the central Cl atom which has a lone pair of electrons as well. Thus, the ClF5 molecule possesses a square pyramidal shape or molecular geometry.
Why is the molecular geometry or shape of ClF5 different from its ideal electron pair geometry?
The electron pair geometry of a molecule only depends on the total number of electron density regions or electron domains around the central atom of the molecule, irrespective of the fact whether it’s a bond pair or a lone pair.
However, its shape or molecular geometry gets strongly influenced based on the distinction between bond pairs and lone pairs.
One lone pair of electrons on central Cl in ClF5 leads to a strong lone pair-bond pair repulsive effect. Thus it occupies a square pyramidal shape as opposed to the ideal octahedral electron geometry.
What is the shape of NH3 and ClF5 using the VSEPR concept?
Ammonia (NH3) has a trigonal pyramidal shape as per the VSEPR concept. There are three H-atoms bonded to the central N-atom and one lone pair of electrons is present on it in the NH3 molecule.
In contrast to that, the chlorine pentafluoride (ClF5) molecule possesses a square pyramidal shape. It also has a lone pair of electrons on the central Cl-atom while five F-atoms are covalently bonded to this atom.
What is the similarity and difference between ClF5 and IF5 shapes and geometry?
Both ClF5 and IF5 are interhalogen compounds, made up of two different kinds of halogens. Both have an octahedral electron geometry and an identical shape or molecular geometry i.e., square pyramidal.
There are a total of 6 electron domains around the central atom in each molecule. Out of which there are 5 bond pairs and 1 lone pair.
The only difference is that ClF5 has chlorine (Cl) at the center while IF5 has an iodine (I) atom present as the central atom.
Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/
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