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Hybridisation

Hybridisation of SiH₄

Si is sp³ hybridised (hybridization by the VSEPR count): 4 sigma bonds and no lone pairs give a tetrahedral shape, bond angle 109.5°.

HHSiHH
  • Si
  • H

SiH₄Silane

Tetrahedral

AB₄: 4 bond pairs, no lone pairs

  • Hybridisationsp³
  • Bond angle109.5°
  • Polaritynon-polar

Why this shape

  1. Si has 4 valence electrons. It uses four in four single bonds to H, so none are left over.
  2. Steric number = four sigma bonds + no lone pairs = 4, so Si is sp³ hybridised.
  3. Four electron pairs point to the corners of a tetrahedron (tetrahedral electron geometry). With no lone pairs the atoms take the same shape: tetrahedral.
  4. All the bond pairs repel each other equally, so the angle is the ideal 109.5°.
  5. The bond dipoles cancel in the symmetric tetrahedral shape, so SiH₄ is non-polar.

Lewis structure

8 valence electrons
SiHHHH

Formal charges: none

Working

Why this hybridisation and shape

  1. Si has 4 valence electrons. It uses four in four single bonds to H, so none are left over.
  2. Steric number = four sigma bonds + no lone pairs = 4, so Si is sp³ hybridised.
  3. Four electron pairs point to the corners of a tetrahedron (tetrahedral electron geometry). With no lone pairs the atoms take the same shape: tetrahedral.
  4. All the bond pairs repel each other equally, so the angle is the ideal 109.5°.
  5. The bond dipoles cancel in the symmetric tetrahedral shape, so SiH₄ is non-polar.

Class 11, Chapter 4 Chemical Bonding and Molecular Structure.

Questions

Hybridisation of SiH4: quick answers

What is the hybridisation of SiH4?

Si has 4 valence electrons. It uses four in four single bonds to H, so none are left over. Steric number = four sigma bonds + no lone pairs = 4, so Si is sp³ hybridised.

What is the shape of SiH4 and its bond angle?

Tetrahedral, with a bond angle of 109.5 degrees. Four electron pairs point to the corners of a tetrahedron (tetrahedral electron geometry). With no lone pairs the atoms take the same shape: tetrahedral. All the bond pairs repel each other equally, so the angle is the ideal 109.5°.

Is SiH4 polar or non-polar?

Non-polar. The bond dipoles cancel in the symmetric tetrahedral shape, so SiH₄ is non-polar.

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