Is SiCl4 a Polar or Nonpolar Substance?

Silicon tetrachloride (SiCl4) is an inorganic chemical used to create highly pure silicon or silica in commercial applications. SiCl4 is made by chlorinating various silicon compounds such as ferrosilicon, silicon carbide, or combinations of silicon dioxide and carbon.

When stored in wet air, SiCl4 is a colourless volatile liquid that generates vapours. SiCl4 reacts violently with water, resulting in white crystalline silicon dioxide and steamy HCl fumes. Water vapour in wet air produces liquid SiCl4 fumes as a result of this.

The polarity of SiCl4 and the factors that influence it are discussed in this article.

Is SiCl4 polar or nonpolar, then? Because of its linear and symmetrical form, SiCl4 is a non-polar molecule. The bonds in the molecule are polar because the chlorine atom is more electronegative than the silicon atom, but the dipoles of both bonds in SiCl4 cancel out due to the linear and opposite orientations of both links. As a result, the net dipole moment is zero, indicating that SiCl4 is non-polar.

Let’s take a closer look at the principles of Polarity.

In nature, why is SiCl4 nonpolar?

Three major points must be examined in order to determine the polarity of any inorganic compound:

The compound’s Lewis structure

The compound’s shape or symmetry

The compound’s net dipole moment

SiCl4 Lewis Structure

Lewis structures, also known as electron-dot structures or electron-dot diagrams, depict the bonding between atoms in a molecule as well as any lone electron pairs present.

Lewis structures can be created for covalently bonded molecules as well as coordination compounds.

Silicon is the central atom in SiCl4, and its four valence electrons share a single bond with the four chlorine atoms surrounding it.

As a result, the silicon atom has no lone pairs of electrons.

Lewis structures reveal how an atom will bond and the number of bonds it will make.

This understanding will eventually aid us in comprehending the forms of molecules as well as their chemical properties.

The symmetry and shape of SiCl4

The polarity of a chemical is also determined by the shape and structure of a molecule.

This claim is backed up by a slew of scientific evidence, ranging from physical attributes to chemical reactivity. The structures of small molecules, especially molecules with a single centre atom, are predictable.

The fundamental notion in molecular structures is valence shell electron pair repulsion (VSEPR). Electron pairs, which are made up of negatively charged particles, are said to reject each other in order to move as far apart as possible.

This gives SiCl4 a tetrahedral structure, with a coordination number of four.

A molecule’s symmetry is determined by the presence of symmetry operations performed on symmetry elements.

A symmetry element is a line, a plane, or a point in or through an object that results in an orientation that is indistinguishable from the original after rotation or reflection.

The polarity of a compound is also heavily influenced by the symmetry of a molecule.

The chlorine atoms in SiCl4 are arranged at an equal distance from each other, allowing the molecule’s distinct structure to be determined.

The Cl atoms are symmetrical in nature because they are at an equal distance from each other and from the centre atom silicon.

In general, when molecules have symmetry, they are predicted to be non-polar in nature. However, in order to be certain, the molecule’s net dipole moment must be examined.

SiCl4 has a net dipole moment.

In the presence of charge separation, the dipole moment is a measure of the polarity of the molecule.

The size of the dipole moment is also influenced by the distance between the charge separations.

Due to variances in electronegativity, they can form in ionic or covalent interactions. The dipole moment increases in proportion to the electronegativity difference.

The electronegativity of the silicon (Si) atom in SiCl4 is 1.9, while the electronegativity of the chlorine (Cl) atom is 3.16. The difference in electronegativity between Si and Cl atoms is approximately 1.26, which is more than 0.4.

As a result, the single bond between Si and Cl is shown to be polar.

When looking at the molecule’s dipole moment, the four single bonds between the Si and Cl atoms behave in the opposite direction.

As a result, the net dipole moment is 0, indicating that there are no poles on this compound. As a result, SiCl4 is classified as a NON-POLAR chemical.

What Is the Difference Between Polar and Nonpolar Molecules?

To build a molecule, chemical substances use a variety of bonds to join their atoms. The development of various types of bonds results in the formation of ionic, hydrogen, covalent, and metallic molecules.

The most prevalent and powerful types of bonding are ionic and covalent connections.

  1. Ionic bond: When two atoms with opposite charges join to create a molecule, an ionic link is produced.

In this situation, two oppositely charged atoms stabilise each other. When the electronegativities of two atoms differ significantly, these linkages are commonly used.

Electrons are entirely transmitted in such bondings.

  1. Covalent bond: When two or more atoms share electrons in order to stabilise one another, a covalent connection is formed.

Depending on the amount of electrons involved, these bonds can be single, double, or triple. These linkages can be either polar or nonpolar in nature.

Polar Molecule: A polar molecule is one in which the charge distribution of two atoms forming a bond is uneven.

One of the atom’s partial ionic charges increases in this situation.

This happens when the electronegativity of the two atoms differs significantly.

As a result, a partial ionic charge is produced, with one atom being negatively charged and the other substantially positively charged, resulting in a polar molecule.

One of the most well-known examples of a polar molecule is NF3. Take a look at the polarity of NF3 paper.

Nonpolar Molecule: A nonpolar molecule is formed when two atoms create a covalent bond that is symmetric and has an equal ionic charge on both atoms.

A non-polar bond is created when the electronegativities of both atoms are the same. BeH2 is an example of such a chemical.

Take a look at the article about BeH2 polarity.

Uses of SiCl4

Semiconducting silicon is made from SiCl4.

It’s utilised to make silica gel, silicic esters, and a ceramic material binder.

Because of its fuming nature, it is utilised in warfare to create smoke screens.

It is crucial in the production of transistors.

It’s utilised to make solar cells and fused silica glass out of exceedingly pure silica.

It’s a chemical that’s used in industries as an adhesive and sealant.

It is utilised in the polysilicon manufacturing process as a reactant or raw ingredient.

For the production of optical fibres, SiCl4 is used as a synthesising material.

General Information about SiCl4

SiCl4 has a molecular weight of 169.9.

It’s a suffocating liquid that’s transparent, colourless, mobile, and fuming.

SiCl4 has a boiling point of 135.7 °F (57 °C) and a melting temperature of -94 °F (-70 °C).

The SiCl4 molecule has an sp3 hybridization.

SiCl4 has a bond angle of 109.5°.

At temperatures above 650°C, it will self-ignite.

SiCl4 is recognised as a skin, ocular, and respiratory system irritant.

Silicon Tetrachloride is a superb water-soluble source of crystalline silicon.

The direct synthesis of silicon tetrachloride by the reaction of chlorine on silicon was phased out worldwide in the early 1980s.

It is non-explosive and non-oxidizing.

SiCl4 is made in a factory.

I SiCl4 can be made by combining silicon with chlorine and exposing it to ultraviolet light.

SiHCl3 + Cl2 → SiCl4 + HCl

SiO2 (s) + 2Cl2 (g) → SiCl4 (g) + O2 (g)

(ii) Silicon carbide can also be converted to SiCl4 by reacting it with hydrogen chloride.

SiCl4 + CH4 SiCl4 + CH4 SiCl4 + CH4 SiCl4 + CH4 SiCl4 + CH4 SiC

(iii) A byproduct of zirconium tetrachloride manufacturing.

ZrSiO 4 + 4C + 4 Cl 2 = ZrCl 4 + SiCl 4 + 4CO

Conclusion

Because of the higher electronegativity difference between Si and Cl, the covalent bonds between them are polar in all forms.

The dipole moment grows in proportion to the electronegativity.

Because the dipole moment in the opposite direction cancels out, the compound as a whole is non-polar.

I hope that this article has given you a better understanding of SiCl4’s polarity and other properties.

Other Related Issues

SiCl4 is a liquid with a low boiling and melting temperature, therefore why is it a liquid?

They are bound together by weak intermolecular interactions because SiCl4 is a covalent combination. As a result, breaking the link between these molecules requires less energy.

This is possible with a low boiling and melting point.

What happens when SiCl4 comes into contact with water?

Orthosilicic acid and hydrogen chloride are formed when silicon tetrachloride combines with water.

SiCl4   +   4H2O   ——>   Si(OH)4   +    4HCl

How can it be safely kept and handled?

It can be properly stored in the absence of air because it has no effect on iron, steel, or common metal alloys, and it can be handled safely with metal equipment.

Read more: Lewis Structure, Molecular Geometry, Hybridization, and the MO Diagram for BrF3.

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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