Numford
Hybridisation

Hybridisation of C₂H₄

Each C atom is sp² hybridised (hybridization by the VSEPR count): 3 sigma bonds and no lone pairs give a trigonal planar shape, bond angle about 120°.

HCHHCH
  • C
  • H

C₂H₄Ethene

Trigonal planar

AB₃: 3 bond pairs, no lone pairs on each C

  • Hybridisationsp²
  • Bond angleabout 120°
  • Polaritynon-polar

Why this shape

  1. Each C has 4 valence electrons. It uses four in one double bond to C and two single bonds to H, so none are left over.
  2. Steric number = three sigma bonds + no lone pairs = 3, so each C is sp² hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.
  3. Three electron pairs point to the corners of a flat triangle (trigonal planar electron geometry). With no lone pairs the atoms take the same shape: trigonal planar.
  4. All the bond pairs repel each other equally, so the angle is the ideal about 120°.
  5. The molecule is flat and symmetric, so the C-H bond dipoles cancel.

Lewis structure

12 valence electrons
CCHHHH

Formal charges: none

Working

Why this hybridisation and shape

  1. Each C has 4 valence electrons. It uses four in one double bond to C and two single bonds to H, so none are left over.
  2. Steric number = three sigma bonds + no lone pairs = 3, so each C is sp² hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.
  3. Three electron pairs point to the corners of a flat triangle (trigonal planar electron geometry). With no lone pairs the atoms take the same shape: trigonal planar.
  4. All the bond pairs repel each other equally, so the angle is the ideal about 120°.
  5. The molecule is flat and symmetric, so the C-H bond dipoles cancel.

Class 11, Chapter 4 Chemical Bonding and Molecular Structure.

Questions

Hybridisation of C2H4: quick answers

What is the hybridisation of C2H4?

Each C has 4 valence electrons. It uses four in one double bond to C and two single bonds to H, so none are left over. Steric number = three sigma bonds + no lone pairs = 3, so each C is sp² hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.

What is the shape of C2H4 and its bond angle?

Trigonal planar, with a bond angle of about 120 degrees. Three electron pairs point to the corners of a flat triangle (trigonal planar electron geometry). With no lone pairs the atoms take the same shape: trigonal planar. All the bond pairs repel each other equally, so the angle is the ideal about 120°.

Is C2H4 polar or non-polar?

Non-polar. The molecule is flat and symmetric, so the C-H bond dipoles cancel.

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