Lewis Structure, Geometry, Hybridization, and Polarity of SiCl2Br2

The inorganic compound SiCl2Br2 dibromo dichlorosilane is made up of silicon and four halogen atoms. Silicon is a metalloid because it possesses both metal and non-metal characteristics. Halogens are non-metallic substances. Chlorine makes up two of the four halogen atoms, while bromine makes up the other two.

258.80 grams/mole is the molecular weight. SiCl2Br2 has a melting point of -45.5°C. All four bonds are covalent and polar.

The ideas needed to predict Lewis structure, geometry, hybridization, and polarity of compounds will be discussed in this article.

Structure of Lewis

The Lewis structure of a compound is a two-dimensional arrangement of electrons, bonds, and atoms. It does not always portray a realistic picture of the compound.

In a stable Lewis structure, all atoms should follow the octet rule and have formal charges.

The Rule of the Octet

This rule applies to the elements of the main group.

Because noble gases are considered stable, all elements desire to have a configuration comparable to that of a noble gas.

Noble gases belong to group 18, and their valence shell structure has eight electrons. As a result, atoms with eight valence electrons are deemed stable.

Charge Formal

It’s a purely theoretical idea.

The neutrality of all atoms in a compound is not guaranteed.

When a charge is spread on constituent atoms, formal charge is created, which displays the charge existing on each atom in a compound.

The formula for calculating it is given below.

Drawing the Lewis structure of SiCl2Br2 in steps

Step 1: Determine the total number of electrons in the valence shell of the chemical.

This is accomplished by adding all of the constituent atoms’ valence shell electrons.

Atomic Number Atomic Number Atomic Number Atomic Number Atomic Number Atomic Number Atom

According to group number, valence electrons

Configuration of electronic devices (E.C.)

E.C.’s Valence Shell

E.C.’s valence electrons

Fourteen Si 14 14 4

3s2 3p2 n=3 1s2 2s2 2p6 3s2 3p2

4

Cl 17 17 7 (two)

n=3 1s2 2s2 2p6 3s2 3p5

7

Br 35 17 7 (two)

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 n=4 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5

7

Total valence shell electrons = 4 + (72) + (72) = 32

For Si, Cl, and Br, the Lewis dot structure is as follows:

Step 2: Pick a good core atom for your chemical.

Out of the constituent atoms, the central atom is meant to be the least electronegative.

The electron density of the core atom is meant to be shared by all other atoms.

The core atom will not share the electron density with side atoms if it is more electronegative than the side atom.

As a result, Si is the compound’s core atom.

Step 3: Sketch down a skeleton diagram.

In this phase, we must properly organise the side and central atoms.

Arrange the valence electrons around the elemental symbols in step four.

Bond formation is used to put the entire valence shell electrons (calculated in step 1).

Step 5: Form bonds to complete the octet of atoms.

In the solitary state, each Cl and Br atom contains seven valence electrons. To complete the octet, they share one electron with Si.

In its isolated state, Si possesses four valence electrons. To complete the octet, it borrows one electron from both Cl and Br atoms.

Step 6: Determine all atoms’ formal charges.

This chemical has a net charge of zero. As a result, the total formal charge on three atoms should equal zero.

Atom

In a free atom, the total number of valence electrons is

Formal Charge*0.5 Total amount of lone pairs (Total number of bonding electrons)

Si 4 0 80.5=4 Si 4 0 80.5=4 Si 4 0 8*0.5

4-0-4=0

Cl1 7 3 80.5=4 Cl1 7 3 80.5=4 Cl1 7 3 8*0.5

7-3-4=0

Cl2 7 3 80.5=4 Cl2 7 3 80.5=4 Cl2 7 3 8*0.5

7-3-4=0

7 3 80.5=4 Br1 7 3 80.5=4

7-3-4=0

7 3 80.5=4 Br2 7 3 80.5=4

7-3-4=0

As a result, the Lewis structure developed in step 5 is the best for SiCl2Br2.

Geometry of SiCl2Br2

For many features of a compound, we cannot rely just on Lewis structure. The VSEPR theory is used to forecast the geometry of covalent compounds.

The 3D arrangement of atoms and bonds is known as geometry.

Some electron pairs aren’t involved in bond formation, but they do have an impact on the arrangement of atoms and bonds. Lone pairs of electrons are such electron pairs, and the distorted geometry is known as shape.

The valence shell electron pair repulsion theory is abbreviated as VSEPR.

The VSEPR theory states that

• Because the valence electron pairs resist each other, the system becomes unstable.

• To make the electron configuration stable, the repulsions between them must be reduced.

• As a result, electrons align themselves with the least amount of repulsion and the greatest distance between them.

• The molecule geometry is determined by the stable arrangement of atoms’ valence electron pairs.

Steps to Predict SiCl2Br2 Geometry Using VSEPR

Step 1: Calculate A by counting the number of valence shell electrons on the centre atom (arbitrary variable).

The core element in SiCl2Br2 is Si, which possesses four valence electrons. (Shown in step 1 of the Lewis structure drawing)

A=4

Step 2: Determine the number of side atoms and multiply by B. (arbitrary variable).

There are four side atoms in SiCl2Br2, two chlorine and two bromine, and B=4.

Step 3: Subtract the charge from B for positively charged compounds and add the charge to B for negatively charged compounds if the chemical is charged.

For neutral substances, this step might be skipped.

There is no charge contribution in SiCl2Br2, and B=6 is the only value.

Step 4: Add the contributions of side atoms and charge to the core atom’s contribution, i.e. A+B.

A+B=8 for SiCl2Br2.

Step 5: Multiply A+B by 2 to get the total number of electron pairs that affect the form.

There are four electron pairs in SiCl2Br2.

Step 6: Separate the total electron pairs into bonding and non-bonding electron pairs. The number of side atoms equals the number of bonding electron pairs.

There are four side atoms in SiCl2Br2. As a result, there are four electron bonding pairs and zero non-bonding pairs.

The following table can be used to forecast geometry and shape based on this information.

Tetrahedral geometry and form characterise electrons. Due to the lack of a lone pair of electrons, the geometry and shape are identical.

Hybridization of SiCl2Br2

Hybridization is a unique idea that explains the geometry and bonding of several polyatomic covalent compounds.

The mixing of atomic orbitals to generate equivalent hybrid orbitals is known as hybridization. It is concerned with energy redistribution.

It is impossible to blend all atomic orbitals. Hybrid orbitals can only be formed when orbitals with identical shapes, sizes, and energies mix.

One 3s and two 3p orbitals, for example, can be merged to generate three sp2 orbitals, but 1s and 5d cannot due to the large energy difference.

The operations are simply carried out on the wavefunction of orbitals; there is no literal mixing of orbitals. Hybridization does not occur in all compounds, as it does in PH3.

The core atom in SiCl2Br2 is Si. Only the centre atom is hybridised in this case.

Si has the electrical structure 1s2 2s2 2p6 3s2 3p2 in its ground state.

Si’s excited state electrical arrangement is 1s2 2s2 2p6 3s1 3p3.

All four electrons are unpaired in an excited state.

With the Si atom, the halogens form a sigma bond. When the connections are created by overlap with 3s and 3p, however, the strength of the sigma bond is different.

Every halogen atom desires an equal amount of overlap.

To make a stable combination, all four silicon orbitals are mixed together to form four equivalent orbitals known as sp3 orbitals.

The Hybridization Calculation Trick

Hybridization can also be predicted by calculating the total electron pairs, which we did in the VSEPR geometry prediction.

In the case of SiCl2Br2, the total domain is 4. Hybridization is sp3 for steric number 4 according to the table.

Polarity of SiCl2Br2

A polar compound is SiCl2Br2.

The existence or absence of a net dipole moment determines a compound’s polarity.

The net dipole moment, in turn, is influenced by a number of parameters, including:

• The individual bond’s dipole moment

• Electronegativities that differ

• Aesthetics

• Aesthetics

S-Br and S-Cl are the two types of bonds in this molecule.

Si, Br, and Cl have electronegativity values of 1.9, 2.96, and 3.16, respectively.

The difference in electronegativity between the Si-Br and Si-Cl bonds is 1.06, whereas the difference in electronegativity between the Si-Br and Si-Cl bonds is 1.26. The bonds take on a polar aspect as a result of the difference in electronegativity.

Polar compounds are not guaranteed by polar bonds. Tetrahedral is the shape. Dipole moments would cancel each other if all side atoms were the same.

Because there are two types of side atoms in this compound, dipole moments are not cancelled, making it an unsymmetrical compound.

As a result, the net dipole moment of SiCl2Br2 is not zero, and the compound is polar.

Conclusion

A covalent molecule is SiCl2Br2.

Because all atoms fulfil the octet rule and satisfy the formal charge of the compound, the Lewis structure predicted is the most stable.

Tetrahedral geometry and shape are the result.

The centre atom is sp3 hybridised.

It’s a polar substance.

Good luck with your reading!

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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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