SiCl4 Lewis Structure: Drawings, Hybridization, Shape, Charges, Pair And Detailed Facts

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In this article, named as “sicl4 lewis structure”, lewis structure, hybridization, geometry, formal charge calculation with some detailed explanations on silicon tetrachloride are discussed briefly.

SiCl4 known as silicon tetrachloride, is a colorless volatile inorganic liquid with a tetrahedral structure and bond angle 109.50. In SiCl4, silicon atom is connected by four bonds with four chlorine atoms. These four bonds are directed towards the corner of a regular tetrahedron.

Let’s focus one the following topics.

How to draw lewis structure for SiCl4?

The structural representation, Lewis structure was first discovered by Gilbert. N. Lewis in the year of 1916 and published in his journal named as “The Atom and the Molecule”. This structural representation is very much significant because formal charge calculation, nonbonding electrons can be determined from it.

Lewis structure is drawn maintaining the following steps-

  1.  Firstly, the number of valance electrons are determined. Silicon (Si) and chlorine have four and seven electrons in their outer most shell or valance shell.
  2. The next step is to calculate the number of bond (covalent or ionic) connectivity between the atoms. In SiCl4, four covalent bonds are present between silicon and chlorine.
  3. The next one is to calculate the nonbonding electrons from total valance electron of each of the respective atoms. Silicon has zero electrons as nonbonded and each of the chlorine atom has six electrons as nonbonding.

The above steps must be followed to draw a lewis structure.

sicl4 lewis structure
SiCl4 Lewis Structure

SiCl4 Lewis Structure Shape

Shape of any molecule can be decided by two factor-

  1. Hybridization
  2. Repulsion

Basically, hybridization decides the geometry of the molecule and repulsive factor decides the shape of the molecule. Repulsive factor can be different types. But only three factors that have a great impact on a shape of the molecule are listed below-

  • Lone pair-lone pair repulsion
  • Lone pair-bond pair repulsion
  • Bond pair-bond pair repulsion

The increasing order in magnitude of the above repulsive factor is-

Bond pair- bond pair repulsion < Bond pair – lone pair repulsion < Lone pair – lone pair repulsion

In SiCl4, central atom (silicon) does not have any lone pair or nonbonding electron. Thus, there is no involvement of lone pair-lone pair repulsion or lone pair – bond pair repulsion. Due to absence of this repulsion, the molecule shows its actual geometrical structure which can be predicted by using only the factor hybridization.

SiCl4 shape jpeg
 Shape of SiCl4.
Image Credit: Wikimedia Commons.

SiCl4 Lewis Structure Formal Charges

One of the most important significant role of lewis structure is that formal charge can be calculated using this structural representation. Formal charge is calculated from the formula described below-

  • Formal charge = Total number of valance electrons – number of electrons remain as nonbonded – (number of electrons involved in bond formation/2)
  • Formal charge of Silicon (Si) = 4 – 0 – (8/2) = 0
  • Formal charge on each of the chlorine atom (Cl) = 7 – 6 – (2/2) = 0

From the above calculation of formal charge it can be decided that the molecule is a charged species or neutral in nature. The calculation makes it clear that SiCl4 is a neutral species.

SiCl4 Lewis Structure Lone Pairs

Lone pairs are those pair of electrons who do not participate in bond formation in a molecule. Thus, the number of nonbonding electrons will be the subtracted produce of total valance electron and number of bonded electron.

  • Lone pair or nonbonded electron = Total number of valance electron – number of bonded electrons.
  • Nonbonded electrons on silicon = 4 – 4 = 0
  • Nonbonded electrons on each of the chlorine atom = 7 – 1 = 6 or 3 lone pairs.

Silicon has total 4 electrons in its valance shell (3s2 3p2). Chlorine is a halogen compound having 7 electrons in its outer most shell (3s2 3p5). Si uses its four electron and chlorine uses its only one electron in bond formation.

SiCl4 Hybridization

Hybridization is defined as the mixing of two or more than two orbitals. Hybridization of any molecule can easily be determined by using VSEPR theory (valance shell electron pair repulsion theory).

The hybridization of silicon in SiCl4 is sp3. Sulfur has total four valance electrons and all these valance electrons are getting paired by the four valance electrons coming from four chlorine atoms. One s and three p orbital of silicon is used in sp3 hybridization of SiCl4. In most of the times hybridization can be predicted from lewis structure. What was predicted from lewis dot structure that silicon has no electron remain as nonbonded is proved in the image of hybridization (shown below). Thus it shows the actual bond angle of tetrahedral structure, that is 109.50.

SiCl4 hybridization
Hybridization of SiCl4

SiCl4 Lewis Structure Octet Rule

Octet rule is defined as the rule of having eight electrons in the valance shell of the respective valance shell to achieve the electron configuration like their nearest noble gas in periodic table. This rule explains the stability of any molecule.

In SiCl4, one silicon atom is attached with four chlorine atoms. There are four electrons in the valance shell of silicon. After forming bond with four chlorine atoms, silicon gains four more electrons in its valance shell. As Silicon tetrachloride is a covalent compound, so, valance electrons are basically shared between the molecules.

Four chlorine atoms also obey the octet rule. They have seven valance electrons and after bond formation with silicon atom, they have gained one electron from silicon as one valance electron from silicon is shared with each of the chlorine atom.

SiCl4 Polar or Nonpolar

SiCl4 is a molecule with zero dipole moment. But the four Si-Cl bonds are comparatively polar due to the electronegativity difference between silicon and chlorine atom (electronegativity of silicon and chlorine is 1.9 and 3.16 in Pauling scale). Polarity not only depends on the presence of polar substituents but also depends on the orientation of the polar groups. The direction of four Si-Cl bonds are almost in anti position with each other. Thus, the dipole moment of each of the four Si-Cl bond is getting cancelled by the other and the resultant dipole moment will be showing zero.

SiCl4 Polarity
SiCl4, a nonpolar molecule

Frequently Asked Questions (FAQ)

Does SiCl4 react with water?

Answer: SiCl4 reacts with water instantly and form silicon dioxide (SiO2) and HCl gas.

Why SiCl4 is easily hydrolyzed than CCl4?

Answer: Silicon has vacant d orbital and thus it can expand its coordination number beyond four. But carbon has no vacant d- orbital to react with water. The lone pairs of oxygen in water are reacted with silicon and easily SiCl4 is hydrolyzed but CCl4 can’t.

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