Numford
Hybridisation

Hybridisation of C₂H₂

Each C atom is sp hybridised (hybridization by the VSEPR count): 2 sigma bonds and no lone pairs give a linear shape, bond angle 180°.

HCCH
  • C
  • H

C₂H₂Ethyne

Linear

AB₂: 2 bond pairs, no lone pairs on each C

  • Hybridisationsp
  • Bond angle180°
  • Polaritynon-polar

Why this shape

  1. Each C has 4 valence electrons. It uses four in one triple bond to C and one single bond to H, so none are left over.
  2. Steric number = two sigma bonds + no lone pairs = 2, so each C is sp hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.
  3. Two electron pairs point in opposite directions, along a line (linear electron geometry). With no lone pairs the atoms take the same shape: linear.
  4. All the bond pairs repel each other equally, so the angle is the ideal 180°.
  5. The molecule is a straight line, so the two C-H bond dipoles cancel.

Lewis structure

10 valence electrons
CCHH

Formal charges: none

Working

Why this hybridisation and shape

  1. Each C has 4 valence electrons. It uses four in one triple bond to C and one single bond to H, so none are left over.
  2. Steric number = two sigma bonds + no lone pairs = 2, so each C is sp hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.
  3. Two electron pairs point in opposite directions, along a line (linear electron geometry). With no lone pairs the atoms take the same shape: linear.
  4. All the bond pairs repel each other equally, so the angle is the ideal 180°.
  5. The molecule is a straight line, so the two C-H bond dipoles cancel.

Class 11, Chapter 4 Chemical Bonding and Molecular Structure.

Questions

Hybridisation of C2H2: quick answers

What is the hybridisation of C2H2?

Each C has 4 valence electrons. It uses four in one triple bond to C and one single bond to H, so none are left over. Steric number = two sigma bonds + no lone pairs = 2, so each C is sp hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.

What is the shape of C2H2 and its bond angle?

Linear, with a bond angle of 180 degrees. Two electron pairs point in opposite directions, along a line (linear electron geometry). With no lone pairs the atoms take the same shape: linear. All the bond pairs repel each other equally, so the angle is the ideal 180°.

Is C2H2 polar or non-polar?

Non-polar. The molecule is a straight line, so the two C-H bond dipoles cancel.

Try any molecule