Bond Types and Hybridization in Acetylene (C₂H₂)

Q1. Identify the types of bonds and the hybrid orbitals involved in the bonding of acetylene (C₂H₂).

Background

Topic: Valence Bond Theory and Hybrid Orbitals

This question tests your understanding of how atomic orbitals hybridize and overlap to form sigma (σ) and pi (π) bonds in molecules, specifically in acetylene (C₂H₂), which features a triple bond between two carbon atoms.

Key Terms and Formulas

• Hybrid Orbitals: Orbitals formed by the mixing of atomic orbitals (e.g., sp, sp², sp³).

• Sigma (σ) Bond: Formed by head-on overlap of orbitals.

• Pi (π) Bond: Formed by side-to-side overlap of p orbitals.

• Bond Types in C₂H₂: 1 σ bond and 2 π bonds between the carbons, plus σ bonds between carbon and hydrogen.

Step-by-Step Guidance

1. Start by identifying the hybridization of each carbon atom in acetylene. Each carbon is bonded to two atoms (one hydrogen and one carbon), so it uses sp hybridization.

2. Recognize that the triple bond between the carbons consists of one σ bond and two π bonds. The σ bond is formed by the overlap of two sp hybrid orbitals from each carbon.

3. The two π bonds are formed by the side-to-side overlap of the unhybridized p orbitals (py and pz) from each carbon atom.

4. The C–H bonds are σ bonds formed by the overlap of an sp hybrid orbital from carbon and the 1s orbital from hydrogen.

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