Chlorine tetrafluoride or ClF5 is a colorless interhalogen compound having a sweet odor and a gaseous state.
It has a 130.445 g/mol molecular weight and a density of 4.5 g/lit. It has a boiling point of 260 K and a melting point of 170 K.
ClF5 can be used as an oxidizer in rockets and propellants due to its property as a strong oxidant. However, it is highly corrosive and toxic in nature. Prolonged exposure to heat can lead to explosions or ruptures of the containers.
Chlorine tetrafluoride is a strong fluorinating agent and is found to react readily with several elements at room temperature.
Preparation of ClF5
ClF3 + F2 ——> ClF5 (at high temperature and high pressure)
Atoms of similar or different elements come together and form a new molecular composition, which creates new chemical compounds. The study of atomic attraction that results in product formation is known as chemical bonding and the bond formed is called a chemical bond. We have several types of bonds – ionic, covalent, metallic, hydrogen, and so on.
Let us now learn the chemical bonding inside a molecule of chlorine tetrafluoride in detail.
ClF5 Lewis Structure
If we want to understand the science behind the chemical bonding of any given molecule, we have to first draw the Lewis Structure diagram.
Lewis Structure is a step-by-step procedure to draw a two-dimensional sketch of a molecule or ionic structure. It gives us a diagrammatic representation of the arrangement or distribution of electrons around the constituent atoms to help us have a simplified idea of bond formation.
Now, we will find out the suitable Lewis Structure diagram for our molecule, ClF5.
At first, we will calculate the total number of valence electrons inside the molecule.
Valence electrons are the outermost shell electrons of an element that we can determine from the atomic number and Periodic table.
A molecule of chlorine tetrafluoride has one atom of chlorine and five atoms of fluorine. Both chlorine and fluorine belong to the group of halogens and therefore present in group 17. Each one of the six atomic elements has 7 valence electrons.
The total number of valence electrons ina ClF5 molecule = 7 + 7*5 = 7 + 35 = 42.
We will now find out which element will take the central position in the molecule. Among Cl and F, Cl is more electropositive than F.
The element having the least electronegativity value is usually the central atom and thus chlorine here becomes the central atom.
We have placed the chlorine atom in the center and the fluorine atoms surrounding it. Now, we will place the valence electrons around the atoms.
Lewis Structure is also known as an electron-dot structure since it uses dot notations to represent the valence shell electrons in the skeletal diagram.
Here, as we can see, we have put all the 42 electrons surrounding the six atoms in ClF5.
Since Chlorine is the central atom here, it will form bonds with all the five Fluorine atoms. We have shown the bonds via straight lines indicating an electron pair each.
Now, we will check the Octet Rule:
According to the octet rule, the elements present in the main groups (group 1-17) of the periodic table have a tendency to achieve the octet configuration of the outermost shell of noble gas elements.
Here, Chlorine and fluorine both elements will tend to attain octet fulfillment of their valence shells.
If we look at the five surrounding fluorine atoms, we can see that each one of them has eight electrons around them, six unbonded and two bonded.
But in the case of chlorine, it has 12 valence electrons around itself, with ten bonded and two unbonded.
This is an example of an exception to the general octet rule i.e. ClF5 cannot obey the octet fulfillment rule.
Before we can finalize our Lewis Structure diagram, we have to check another concept: Formal Charge.
Formal charge deals with the charge assigned to atoms inside a molecule if we assume that electrons are always shared equally among them.
This is how we calculate the formal charge values of each atomic element.
In the case of all the five F atoms, the formal charge of each = 7 – 0.5*2 – 6 = 0.
The formal charge value of Cl atom = 7 – 0.5*10 – 2 = 0.
Atoms of both the elements are present in their least possible formal charge values. Therefore, the correct and suitable Lewis Structure diagram of ClF5 is:
ClF5 Molecular Geometry
VSEPR stands for Valence Shell Electron Pair Repulsion theory.
This model is used to explain and predict the 3-dimensional molecular geometry of different molecules (usually covalent bonded). It is an extension of the Lewis Structure concept which can only depict the 2-dimensional sketch but fail to go beyond that.
Through VSEPR theory, we can visualize the electronic arrangement and structural configuration of a molecule in a far better manner.
According to this theory, since electrons are all negatively charged particles, like charges repel each other, and to minimize this repulsion the atoms are spread apart from each other.
For example, a diatomic molecule always usually has a linear molecular geometry having a 180-degree bond angle. Let us now find out the 3D molecular geometry of Chlorine Tetrafluoride with the help of the VSEPR model.
This is an image example of the VSEPR chart. In this theory, we use certain notations to find out the exact molecular shape.
We have VSEPR notation: AXnEx.
A: central atom, here, Chlorine is the central atom.
X: surrounding atoms, ‘n’ represents the number, ∴ n = 5.
E: lone pairs on A, ‘x’ represents the number, ∴ x = 1.
ClF5 molecule has an AX5E1 VSEPR notation. Therefore, the shape is square pyramidal and we have an asymmetrical arrangement.
In quantum mechanics, we have the concept of orbitals. Orbital refers to the mathematical function of the probability of electron presence in a certain region of space. We have atomic orbitals where electrons are present.
Orbital hybridization refers to the combination and fusion of atomic orbitals of the atom inside a molecule to form hybrid orbitals.
In ClF5, we have five single bond formations between Cl and each F atom.
Single bond refers to sigma pair whereas double bond refers to one sigma pair and one pi pair. The electronic configuration of Cl: 1s2 2s2 2p6 3s2 3p5.
Steric Number is a term used in chemistry which is said to be the sum of the number of sigma bonds surrounding the central atom and the number of lone pairs of electrons on that atom.
Steric number = Number of atoms bonded to central atom inside a molecule + Number of lone pair of electrons attached to the central atom
steric number = 5 + 1 = 6.
Accordingly, the hybridization of Cl in ClF5 is sp3d2.
In a bond, when two atomic elements have a considerable difference in their electronegativity values (more than 0.4-0.5), it results in an electric dipole moment. The bond then is known as a polar bond. However, when the difference is not significant enough, the bond is called non-polar.
As we can understand, the term polarity is therefore related to the charge separation between atoms in a molecule.
We can call a molecule polar if it has polar bonds with one positive and one negative end and the symmetry is not linear therefore the dipoles do not get canceled out.
A molecule having polar bonds however can turn out to be non-polar due to symmetrical charge distribution which results in net-zero dipole, for example, Boron trifluoride (BF3).
Is ClF5 polar or non-polar? Let us look at the Pauling electronegativity chart to find out.
Cl has a value of 3.16 whereas F has a value of 3.98. The difference is around 0.82. Therefore, the Cl-F bonds are polar.
Also, the molecule is asymmetrical due to the presence of a lone pair on Cl. This makes the molecule polar in nature.
In this article on ClF5, we have covered the nature of chemical bonding in detail. We have discussed Lewis Structure diagrams, molecular geometry, Polarity, and hybridization.