chemcheat

SiCl4 Lewis Structure

Silicon tetrachloride · A precursor to ultrapure silicon and to optical fibre.

Lewis structure of SiCl4 (Silicon tetrachloride)The bond dipoles are all the same size and the shape places them symmetrically around the central Si, so they cancel exactly.SiClClClCl

The SiCl4 Lewis structure has 32 valence electrons, drawn as four Si–Cl bonds, with twelve lone pairs in total. The central Si is sp3 hybridized, which makes it a tetrahedral molecule with a bond angle of 109.5 degrees. SiCl4 is nonpolar: the bond dipoles are all the same size and the shape places them symmetrically around the central Si, so they cancel exactly.

Calculated properties

Calculated properties of SiCl4
Total valence electrons 32
Bonding electrons 8 (4 shared pairs)
Nonbonding electrons 24 (12 lone pairs)
Lone pairs on Si 0
Electron domains (steric number) 4
VSEPR notation AX4
Electron geometry tetrahedral
Molecular geometry tetrahedral
Bond angle 109.5°
Hybridization sp3
Polarity nonpolar
Formal charges all zero
Resonance structures none
Molar mass 169.885 g/mol

How to draw the SiCl4 Lewis structure

  1. Count the valence electrons

    Add up the outer-shell electrons every atom brings. That total is the budget for the whole structure - every line and every dot has to come out of it, and nothing may be added.

    4 (Si) + 4 x 7 (Cl) = 32 valence electrons

  2. Choose the central atom

    Si is the least electronegative atom here, so it takes the centre. Hydrogen is never central: it can only form one bond.

  3. Join everything with single bonds first

    Every connection starts as one shared pair. Draw them all before worrying about double bonds - the arithmetic in the next step is what tells you where the double bonds have to go.

    4 bonds x 2 = 8 electrons used, 24 left

  4. Work out how far short you are

    Add up what every atom still needs to fill its shell - eight electrons for most atoms, two for hydrogen - minus what its single bonds already give it. Compare that with the electrons you have left. The difference decides everything that follows.

    needs 24, has 24, exactly enough

  5. Fill in the lone pairs

    Every electron not in a bond sits as a lone pair on an atom. Each atom takes exactly what it needs to finish its shell - there is no choice left at this point.

    Cl1: 3, Cl2: 3, Cl3: 3, Cl4: 3 (24 electrons)

  6. Check the central atom

    Si ends up with a full octet. Every electron in the budget is now placed.

    Si: 8 bonding + 0 nonbonding = 8

  7. Check the formal charges

    Formal charge is valence electrons, minus lone-pair electrons, minus the number of bonds. Every atom here comes out at zero, which is the sign of a good structure.

    all formal charges = 0

  8. Work out the shape

    Count the electron domains on Si: 4 bonded groups. A double or triple bond still counts as one domain, because it points in one direction. That gives tetrahedral electron geometry; ignore the lone pairs and the atoms themselves sit in a tetrahedral arrangement.

    steric number 4 -> sp3 -> tetrahedral, bond angle 109.5

  9. Decide whether it is polar

    The bond dipoles are all the same size and the shape places them symmetrically around the central Si, so they cancel exactly.

    dipoles cancel -> nonpolar

Is SiCl4 polar or nonpolar?

SiCl4 is nonpolar. The bond dipoles are all the same size and the shape places them symmetrically around the central Si, so they cancel exactly.

BondElectronegativity differenceCharacter
Si–Cl 1.26 polar covalent
Why this molecule gets set as a problem: Tetrahedral and nonpolar, one period below carbon tetrachloride.

Common questions

How many valence electrons does SiCl4 have?

SiCl4 has 32 valence electrons. 8 of them are in bonds and 24 sit in lone pairs.

What is the molecular geometry of SiCl4?

SiCl4 is a tetrahedral molecule. The central Si has 4 bonded groups, a steric number of 4, which gives tetrahedral electron geometry and a tetrahedral molecule.

What is the bond angle in SiCl4?

The bond angle in SiCl4 is 109.5 degrees. That is the ideal tetrahedral angle, and nothing distorts it here.

What is the hybridization of SiCl4?

The central Si in SiCl4 is sp3 hybridized. Steric number 4 means 4 orbitals have to be mixed, which is exactly what sp3 gives you.

Is SiCl4 polar or nonpolar?

SiCl4 is nonpolar. The bond dipoles are all the same size and the shape places them symmetrically around the central Si, so they cancel exactly.

How this page was produced. The formula was parsed, the connectivity resolved (central atom), and every bond-order arrangement enumerated and scored on octet satisfaction, formal charge and where that charge sits. The structure above is the winner. Bond angles, hybridization and the polarity verdict are read off the resulting geometry, not looked up.