The present article is about ClF5 (Chlorine Pentafluoride) which is an interhalogen compound. Let’s know some interesting facts about this compound.
In the ClF5 Lewis structure, central Chlorine (Cl) atom is bonded to 5 fluorine(F) atoms by single bonds. The ClF5 molecule contains 16 lone pairs, each Fluorine atom has 3 lone pairs and one lone pair is present on the chlorine atom.
| Molecular Name | Chlorine Pentafluoride |
| Chemical Formula | ClF5 |
| Central atom of the lewis structure | Chlorine |
| Number of lone pairs on central atom | 1 |
| Molecular Geometry of OF2 | Square pyramidal |
| Electron Geometry of OF2 | octahedral |
| Bond Angle (Cl – F) | 90 degree |
| No. of valence electron for ClF5 | 42 |
| The formal charge of ClF5 molecule | 0 |
| Hybridization of central atom | sp3d2 |
| Solubility | Reacts with water |
| Nature | Neutral compound |
| Nature of bonds | Covalent bonds |
How many valence electrons are present in the ClF5 Lewis structure?
In the ClF5 molecule, chlorine atom as well as the fluorine atom has 7 electrons in its valence shell.
Calculating valence electrons in ClF5 molecule-
| Atoms in ClF5 | Valence Electrons | Number of atoms in ClF5 | Total Electrons |
| Chlorine | 7 | 1 | 7*1 = 7 |
| Fluorine | 7 | 5 | 7*5 = 35 |
| 42 |
Thus,
in ClF5 molecule there are total 42 valence electrons.
Steps to draw Lewis structure of ClF5
The step-by-step explanation to draw the Lewis diagram of ClF5 –
Step 1: Calculate total valence electrons present in ClF5 molecule
We will start by finding the number of valence electrons in ClF5 molecule.
(Valence electrons are the number of electrons present in the valence shell of an atom)
Both the elements that is Fluorine and Chlorine belongs to group 17th so number of valence electrons for both Chlorine and Fluorine is 7.
Calculating valence electrons in ClF5 –
| Atoms in ClF5 | Valence Electrons | Number of atoms in ClF5 | Total Electrons |
| Chlorine | 7 | 1 | 7*1 = 7 |
| Fluorine | 7 | 5 | 7*5 = 35 |
| 42 |
Step 2: Decide the central atom
While drawing the Lewis dot structure always keep the least electronegative atom in the centre.
As we know that electronegativity increases in a period from left to right and decreases from top to bottom in a group so chlorine is less electronegative than fluorine.
Note: Fluorine is the most electronegative element in the periodic table
keep the least electronegative atom Chlorine in the centre and the 5 Fluorine atom surrounding it and draw the skeletal structure for ClF5 molecule.
Step 3: Either put a bond or electron pair between Cl and F atom
Put two electrons (electron pair) between Chlorine and Fluorine atoms to denote a chemical bond.
Step 4: Make the outer atoms happy by completing their octet
Main group elements got happy when they have attained octet configuration of their nearest noble gas element (18th group). This is what we call as Octet Rule (Exception: hydrogen completes the duplet configuration like that of the noble gas He).
Step 5: Put the remaining electrons on the central atom:
ClF5 has 42 valence electrons, out of which 10 electrons are used in forming bonds between Cl and F while 30 electrons are present as lone pairs on the surrounding 5 fluorine atoms and two electrons are left.
we will now keep these two electrons on the central Chlorine atom.
Step 6: Check formal charge value
Before confirming this as our final Lewis structure diagram, we will check for the formal charge of each atomic element in the ClF5 molecule.
Formal charge = Valence electrons – 0.5 * bonding electrons – non-bonding electrons
For the central atom Chlorine –
Number of non-bonding electrons of chlorine = 2
Number of bonding electrons of chlorine = 10
Formal Charge for Chlorine = 7 – 0.5*10 – 2 = 0
For the outer atoms Fluorine –
Number of non-bonding electrons of fluorine = 6 (3 lone pairs)
Number of bonding electrons of fluorine = 2
Formal charge for fluorine atom =7 – 0.5*2 – 6 = 0
As the F and O elements have least possible formal charges, that means we have obtained our perfect Lewis structure.
What is the formal charge of atoms present in the Lewis Structure ClF5 molecule?
Formal charge is the electric charge given to an atom in a molecule when all of the electrons in a bond are shared equally or while ignoring the electronegativity difference of atoms.
Formal charge = Valence electrons – 0.5 * bonding electrons – non-bonding electrons
For the central atom Chlorine –
Number of non-bonding electrons of chlorine = 2
Number of bonding electrons of chlorine = 10
Formal Charge for Chlorine = 7 – 0.5*10 – 2 = 0
For the outer atoms Fluorine –
Number of non-bonding electrons of fluorine = 6 (3 lone pairs)
Number of bonding electrons of fluorine = 2
Formal charge for fluorine atom =7 – 0.5*2 – 6 = 0
Does ClF5 is an exception to octet rule?
As per the octet rule, main group elements tries to get an octet configuration of their nearest noble gas element. In ClF5 molecule, all the 5 Fluorine atoms attain their octet. All the 5 Fluorine atoms have three non-bonded pairs and a bonded pair around them.
But the central Chlorine atom has five bonded pairs and one lone pair around it, making total surrounding electrons 12.
Thus, ClF5 molecule is an exception to the octet rule.
Why is the Electron Geometry of ClF5 is octahedral though the molecule has a square pyramidal geometry?
ClF5 molecule has 42 valence electrons.
Out of 42 electrons –
- 10 electrons are present as bonded pairs between fluorine and chlorine atoms
- 30 electrons are present as lone pairs on the five Fluorine atoms.
- Two electrons are present on central atom Chlorine as lone pairs.
As electron geometry is found by considering both the bonded pairs and lone pairs in a molecule so the electron geometry of Clf5 molecule is square pyramidal.
Why is the bond angles in ClF5 are slightly less than 90 degrees and not exactly 90 degrees?
Due to the presence of lone pair on the central chlorine atom which causes repulsion with the bond pairs, the bond angle of axial and equatorial F gets distorted which results in less than 90 degrees bond angles.
Thus the bond angles in ClF5 are slightly less than 90 degrees.
How to find out molecular/Electron geometry of ClF5 molecule?
To answer this question, we will use VSEPR model –
The long form of VSEPR is Valence Shell Electron Pair Repulsion theory
By using VSEPR theory, we can know the 3-dimensional molecular geometry of any molecule which we can’t do by using the Lewis Structure which can only predicts the 2-dimensional geometry.
Geometry of ClF5 can be found out by the following ways –
1)Number of lone pairs present on the Chlorine (Cl) in its Lewis structure is –
Lone pair = 0.5*(valence electrons On Cl – No. of Atoms attached to Cl)
= 0.5*(7-5)
= 1
2) Hybridization of Chlorine atom –
Hybridization of Chlorine in ClF5 is –
Hybridization number = No. of atoms attached to Cl + NO. of lone pairs on Cl
= 5 + 1
= 6
As the hybridization number of 6 so the hybridization of ClF5 molecule is sp3d2
3) Using VSEPR notation to get the molecular geometry –
Now the VSEPR notation is AXnEx
AXnEx notation
Where,
A is the central atom
(In ClF5, chlorine is the central atom)
X are the atoms bonded to the central atom,
(In ClF5, F are the atoms bonded to the central atom)
n is the number of atoms
(In ClF5, n=5)
E is lone pairs of electrons present on the central atom
x is the number of lone pairs
(In ClF5, x=1)
So, for ClF5 molecule AXnEx formula is AX5E1
According to VSEPR chart, the molecule with AX5E1 formula has molecular shape as Square Pyramidal.
| Total Domains | General Formula | Bonded atoms | Lone Pairs | Molecular Shape | Electron Geometry |
| 1 | AX | 1 | 0 | Linear | Linear |
| 2 | AX2 | 2 | 0 | Linear | Linear |
| AXE | 1 | 1 | Linear | Linear | |
| 3 | AX3 | 3 | 0 | Trigonal Planar | Trigonal Planar |
| AX2E | 2 | 1 | Bent | Trigonal Planar | |
| AXE2 | 1 | 2 | Linear | Trigonal Planar | |
| 4 | AX4 | 4 | 0 | Tetrahedral | Tetrahedral |
| AX3E | 3 | 1 | Trigonal Pyramid | Tetrahedral | |
| AX2E2 | 2 | 2 | Bent | Tetrahedral | |
| AXE3 | 1 | 3 | Linear | Tetrahedral | |
| 5 | AX5 | 5 | 0 | Trigonal bipyramid | Trigonal bipyramid |
| AX4E | 4 | 1 | See Saw | Trigonal bipyramid | |
| AX3E2 | 3 | 2 | T Shape | Trigonal bipyramid | |
| AX2E3 | 2 | 3 | Linear | Trigonal bipyramid | |
| 6 | AX6 | 6 | 0 | Octahedral | Octahedral |
| AX5E | 5 | 1 | Square pyramid | Octahedral | |
| AX4E2 | 4 | 2 | Square planar | octahedral |
As ClF5 has AX5E1 notation so the molecular geometry of ClF5 is Square Pyramidal
Square pyramidal geometry of ClF5
Why is ClF5 a polar molecule?
A molecule is called polar when –
- Electronegativity difference between the bonded atoms is more than O.4
- It contains a polar bond with a positive and a negative end.
- It has unsymmetrical geometry so the dipoles do not get cancelled.
But sometimes molecule with polar bond can turn out to be non- polar due to the symmetrical distribution of charges so resultant dipole moment is 0.
Chlorine Pentafluoride (ClF5) is a polar molecule because of the following reasons –
- Electronegativity difference between Chlorine (Electronegativity 3.16) and Fluorine (Electronegativity 3.98) is 0.82
- ClF5 is an unsymmetrical molecule as central atom Chlorine has lone pair present on it.
Hybridization in ClF5
Hybridization is the fusion of atomic orbitals of the atom in a molecule to form orbitals of equal energy and orientation
In ClF5, the central Chlorine atom forms five single bonds with 5 fluorine atoms and a lone pair is present on it.
To form bonds with fluorine atoms, the orbitals of Chlorine atom undergoes hybridization .
The ground state electronic configuration of chlorine and fluorine are –
Chlorine (ground state): 1s2 2s2 2p6 3s2 3p5
Fluorine (ground state): 1S2 2S2 2P5
Electronic configuration of Chlorine after gaining electrons by forming bonds with fluorine-
Chlorine 1s2 2s2 2p6 3s2 3p5
Steric Number = Number of sigma bonds surrounding the central atom + Number of lone pairs of electrons on the central atom
Steric Number = 5 + 1 = 6
So, hybridization for chlorine in the ClF5 molecule is Sp3d2
Does ClF5 exhibits resonance?
A molecule can exhibit resonance when –
- There is an interaction between two pi-bond in the molecule
or
- There is an interaction between a pi bond and a lone of electrons present on an adjacent atom in a molecule.
ClF5 do not show resonance as there are no pi-bonds present in ClF5 molecule.
Why is Chlorine Pentafluoride a covalent compound even though it contains electronegative atoms?
As the electronegativity difference between the halogens, Chlorine and Fluorine is low so ClF5 is a covalent compound.
Is ClF5 neutral in nature?
Yes, ClF5 is a neutral in nature containing two different halogen atoms -One Chlorine and five Fluorine atoms.
Conclusion:
Chlorine Pentafluoride is an interhalogen compound. It does not follow the octet rule. It has a square pyramidal geometry. ClF5 is a polar molecule with a dipole moment of 0.82D. It does not show resonance.It is neutral in nature.
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Hi…I am Sonali Jham. I have done my Post-Graduation in Chemistry and also completed B. Ed. I am a Teacher and a Dietician by profession.
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