C2H2 Lewis Structure
Acetylene (ethyne) · The fuel in an oxy-acetylene welding torch.
The C2H2 Lewis structure has 10 valence electrons, drawn as one C≡C bond and two bonds to hydrogen, with zero lone pairs in total. The central C is sp hybridized and the molecule is linear, with a bond angle of 180 degrees. C2H2 is nonpolar: the bond dipoles and lone pairs are arranged symmetrically, so the vectors cancel and the molecule has no net dipole.
- 10 valence e−
- linear
- 180° bond angle
- sp
- nonpolar
Calculated properties
| Total valence electrons | 10 |
|---|---|
| Bonding electrons | 10 (5 shared pairs) |
| Nonbonding electrons | 0 (0 lone pairs) |
| Lone pairs on C | 0 |
| Electron domains (steric number) | 2 |
| VSEPR notation | AX2 |
| Electron geometry | linear |
| Molecular geometry | linear |
| Bond angle | 180° |
| Hybridization | sp |
| Polarity | nonpolar |
| Formal charges | all zero |
| Resonance structures | none |
| Molar mass | 26.038 g/mol |
How to draw the C2H2 Lewis structure
-
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.
2 x 4 (C) + 2 x 1 (H) = 10 valence electrons -
Work out what is bonded to what
The two C atoms bond to each other and split the hydrogens evenly between them.
-
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.
3 bonds x 2 = 6 electrons used, 4 left -
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 8, has 4, short by 4 -
Turn the shortfall into multiple bonds
Being short means atoms have to share more. Every pair that moves from a lone pair into a bond counts twice - once for each atom - so a shortfall of 4 is covered by 2 extra shared pairs. That is where the triple bond comes from.
C1#C2 -
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 -
Work out the shape
Count the electron domains on C: 2 bonded groups. A double or triple bond still counts as one domain, because it points in one direction. That gives linear electron geometry; ignore the lone pairs and the atoms themselves sit in a linear arrangement.
steric number 2 -> sp -> linear, bond angle 180 -
Decide whether it is polar
The bond dipoles and lone pairs are arranged symmetrically, so the vectors cancel and the molecule has no net dipole.
dipoles cancel -> nonpolar
Is C2H2 polar or nonpolar?
C2H2 is nonpolar. The bond dipoles and lone pairs are arranged symmetrically, so the vectors cancel and the molecule has no net dipole.
| Bond | Electronegativity difference | Character |
|---|---|---|
| C–H | 0.35 | nonpolar covalent |
| C–C | 0.00 | nonpolar covalent |
Common questions
How many valence electrons does C2H2 have?
C2H2 has 10 valence electrons. 10 of them are in bonds and 0 sit in lone pairs.
What is the molecular geometry of C2H2?
C2H2 is a linear molecule. The central C has 2 bonded groups, a steric number of 2, which gives linear electron geometry and a linear molecule.
What is the bond angle in C2H2?
The bond angle in C2H2 is 180 degrees. That is the ideal linear angle, and nothing distorts it here.
What is the hybridization of C2H2?
The central C in C2H2 is sp hybridized. Steric number 2 means 2 orbitals have to be mixed, which is exactly what sp gives you.
Is C2H2 polar or nonpolar?
C2H2 is nonpolar. The bond dipoles and lone pairs are arranged symmetrically, so the vectors cancel and the molecule has no net dipole.