Geometry, Hybridization, and Polarity of SeF4 Lewis Structure

Paul Lebeau was the first to synthesise selenium tetrafluoride in 1907. It’s an inorganic chemical that reacts quickly with water.

It’s a toxic liquid with a reputation for acting as a selective fluorinating agent, particularly in organic synthesis reactions.

Electrons of Valence

The valence electrons are the electrons that are the furthest from an atom’s nucleus, i.e. the electrons that are present in the valence shell.

These electrons play an active role in the chemical bonds that an atom creates with other atoms, as well as being given away (or taken up) from one atom to another in ionic bonding.

The Rule of the Octet

Noble gases are the most stable elements in the periodic table because their characteristics are not easily harmed by reactions with other atoms.

All noble gases, with the exception of helium, have eight electrons in their outermost shell. As a result, when an atom of any element possesses eight valence electrons, it is determined that it is stable. The octet rule is the name for this rule.

All atoms, according to this rule, tend to create chemical connections with other atoms by sharing, donating, or accepting electrons from their valence shells in order to complete their octet or gain eight valence electrons in order to achieve stability.

Lewis Structure of SeF4

Gilbert N. Lewis introduced Lewis structures in 1916. They pioneered the practise of depicting atoms as atomic symbols with their valence electrons depicted as dots surrounding them.

It seeks to build the most stable structure for a molecular with formal charge closest to zero and electronic configuration of valence shell closest to 8, i.e. in compliance with the octet rule, much like any other technique of describing molecular structures.

Electron dot structures, also known as Lewis dot structures, are a type of electron dot structure.

SeF4’s Lewis structure is as follows:

The octet for all five atoms bound to create the SeF4 molecule is satisfied in the structure, indicating that the electronic configuration of all four fluorine atoms as well as the selenium atom is eight.

Drawing the Lewis Structure of SeF4 in Steps

Let’s take a look at how to draw the Lewis structure for the SeF4 molecule step by step:

• To begin, we’ll count the number of valence electrons in each of the atoms in the molecule.

Because selenium is a group 16 element, its valence shell has 6 electrons, but fluorine is a group 17 element, hence all fluorine atoms have 7 valence electrons.

As a result, selenium lacks two electrons in order to obtain its octet, whereas fluorine atoms just require one electron apiece.

Now, for the SeF4 molecule, count the total amount of valence electrons:

Selenium has six electrons in its valence.

Fluorine has a valence electron count of seven.

7 X 4 = 28 for 4 fluorine atoms

As a result, the total number of valence electrons is equal to 28 + 6 = 34.

• In the second stage, we’ll pick a molecule’s core atom. All of the other atoms in a molecule are considered to be bound to the centre atom.

The centre atom is usually the atom with the least electronegative charge. Because selenium is less electronegative than fluorine, it is chosen as the centre atom in selenium tetrafluoride.

A single connection connects all four fluorine atoms to the selenium atom.

• The preceding procedure allows us to compute the amount of electrons required to complete an octet for all of the atoms in the molecule.

Every single bond shows the presence of two electrons that are shared. Because fluorine already possessed seven valence electrons, the octet for all four fluorine atoms is completed by sharing one electron each from the selenium atom, giving selenium a total of ten electrons in its valence shell, which is more than typical.

• You might be wondering how selenium can have 10 valence electrons while the maximum number of electrons allowed in an atom’s valence shell is 8.

The concept of “Expanded Octet” is the answer to this question.

• In fact, noble gases and other elements in the periodic table have the ability to expand their octet beyond the conventional limit, allowing them to contain more than 8 electrons in their valence shell.

The presence of an available d energy sublevel is the rationale for this privilege.

Because selenium is one of the privileged atoms, the SeF4 molecule can contain a total of 10 valence electrons.

• As a result, the Lewis structure for Selenium Tetrafluoride is as follows:

• We will calculate the formal charge on the molecule to ensure that the lewis structure sketched is the best possible depiction of the structure of that particular molecule.

It is a hypothetical idea that asserts that a molecule must have the formal charge closest to zero in order to have a stable Lewis structure.

Every atom in the molecule is computed separately.

The formal charge formula is as follows:

[Total number of valence e– in Free State] – [Total number of non-bonding pair electrons (lone pair) – 1/2 (Total number of bonding e–)] Formal Charge = [Total number of valence e– in Free State] – [Total number of non-bonding pair electrons (lone pair) – 1/2 (Total number of bonding e–)]

The formal charge of the SeF4 molecule is calculated as follows:

For the atom of selenium:

FC = [6] – [2] – 12 [8] FC = [6] – [2] – 12 FC = [6] – [2] – 12 FC

As a result, the formal charge on selenium is zero.

Now, let’s look at the fluorine atom:

FC = [7] – [6] – 12 [1] FC = [7] – [6] – 12 [1] FC = [7] – [6]

As a result, FC on Fluorine = 0.

As a result, the molecule’s total formal charge is 0, suggesting that it is the best Lewis structure imaginable.

Check out the SF4 Lewis Structure article.

Molecular Geometry of SeF4

How can you tell if GeF 4, SeF 4, and XeF 4 have the correct molecular shapes? | Socratic

The Valence Shell Electron Pair Repulsion (VSEPR) Theory is used to calculate a molecule’s molecular geometry.

According to this idea, in order to prevent inter-electronic forces, the electrons inside a molecule tend to arrange themselves as far apart as feasible.

Inter-electronic repulsion is thought to exist between electrons of the same atom as well as electrons of other atoms, with inter-electronic repulsion being strongest between lone pairs of electrons since they are free to travel in space.

The driving force for repulsion is the difference in electronegativity of the interacting atoms.

When no repulsive forces are present, the Lewis structure depicted above is the optimal structure for the SeF4 molecule.

However, due to the many forces that are active inside the molecule and change its form and structure, the perfect state does not occur in reality.

The repulsive forces between bonding and non-bonding pairs of electrons dictate the actual structure of a molecule, according to the VSEPR hypothesis.

Selenium is the core atom in Selenium tetrafluoride, to which four fluorine atoms are connected by a single bond.

On the selenium atom, there is also one lone pair of electrons. All of these electrons are pushing each other as hard as they can.

The repelling force decreases in the following order:

Lone pair vs. lone pair > Lone pair vs. bond pair vs. bond pair vs. bond pair vs. bond pair vs. bond pair v

As a result, the bond pairs in the SeF4 molecule get closer to each other and to the greatest distance feasible from the lone pair of electrons, resulting in the molecule’s see-saw form.

The SeF4 molecule has a trigonal bipyramidal electronic geometry and C2V molecular symmetry.

There are two axial and two equatorial bonds in this structure. The axial Se-F bond has a bond length of 177 pm and a bond angle of 169.2° between F-Se-F, while the equatorial Se-F bond has a bond length of 168 pm and a bond angle of 100.6° between F-Se-F.

Hybridization of SeF4

The intermixing of orbitals with similar energy levels produces hybrid orbitals. Hybridization is the term for this procedure.

Linus Pauling coined the term “hybridization” in 1931.

The hybrid orbital gets its name from the fact that the orbitals are blended for formation. The term sp for a hybrid orbital, for example, denotes that one s and one p orbital were mingled together during the hybridization process.

Any molecule’s hybridization state is obtained by computing the steric number from its bonding and non-bonding electrons using the formula below:

The number of sigma () bonds on the centre atom plus the number of lone pairs on the central atom equals the steric number.

Selenium tetrafluoride is a kind of selenium tetrafluoride.

The number of sigma bonds is equal to four.

The number of lone pairs is equal to one.

As a result, the Steric number is 5.

The hybridization state of a molecule is described in the table below based on its steric number:

Steric numberHybridization State
1S
2Sp
3Sp²
4Sp³
5Sp³d
6Sp³d²

Because the steric number of the SeF4 molecule is 5, it has a steric number of 5. As a result, it can be determined that it has an sp3d hybridization state using the table above.

Let’s try to figure out what Selenium tetrafluoride’s hybridization state is.

• Selenium has an sp3 hybridization state in its natural state, which can be expressed as follows:

• The valence electrons are dispersed between the 4s and 4p orbitals, with the 4d orbital remaining empty.

• One electron from the 4p orbital jumps into the 4d orbital as the Selenium atom is stimulated. The 4s orbital, on the other hand, is unaffected because just four fluorine atoms must be linked.

• While the two electrons in the 4s orbital do not participate in bonding, these four excited unpaired electrons form a sigma bond with the four fluorine atoms.

• As a result, the hybridization of the SeF4 molecule becomes sp3d with four sigma bonds and one lone pair of electrons.

• The presence of unoccupied 4d orbitals in selenium’s outermost shell allows it to have an enlarged octet, allowing it to accommodate more than 8 electrons.

SeF4’s polarity

The electronegativity differential between the bonding atoms causes a molecule’s polarity.

It describes the formation of a partial positive charge on one atom and a partial negative charge on another as a result of unequal electron sharing between these atoms.

When the electronegativity difference between the two bonding atoms exceeds 1.5, the molecule becomes polar.

However, in the case of a molecule with uniform geometry, the charges cancel out, however if the molecular structure is distorted due to an unequal distribution of charges, the molecule has a net dipole moment.

The electronegativity of the fluorine atom in the SeF4 molecule is 4, while that of the selenium atom is 2.4.

As a result, the electronegativity difference is 1.6, which is greater than 1.5, suggesting that the fluorine atom develops partial negative charge while the selenium atom develops partial positive charge.

Furthermore, the SeF4 molecule’s structure is altered, implying that the molecule has a net dipole moment.

Properties

The table below lists a handful of Selenium tetrafluoride’s most important properties:

NameSelenium Tetrafluoride
Molecular weight154.954 g/mol
Boiling Point101 °C
Melting Point−13.2 °C
Molecular GeometrySee-saw
Electronic GeometryTrigonal bipyramidal
Molecular SymmetryC2V

Conclusion

Selenium tetrafluoride’s Lewis structure is as follows:

SeF4 has a see-saw molecular geometry, trigonal bipyramidal electronic geometry, and C2V molecular symmetry.

The SeF4 molecule has a steric number of 5 and a hybridization state of sp3d.

The SeF4 molecule is polar due to the electronegativity mismatch between the Selenium and fluorine atoms.

Good luck with your studies!!

Read more: Is CF4 a Polar or Nonpolar Compound?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.

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