C in C2H2 gets SP hybridization, why?

In $C X_{2} H X_{2}$ (acetylene), each carbon atom undergoes sp hybridization due to the following reasons:

sp Hybridization in Ethyne (C₂H₂)sp Hybridization in Ethyne (C₂H₂)

Each carbon in C₂H₂ forms two σ-bonds (with H and C) and two π-bonds (triple bond), requiring sp hybridization (linear geometry, 180° bond angles).

Electronic Configuration and Bonding Requirement:
- Each carbon atom in $C X_{2} H X_{2}$ has two unpaired electrons in its valence shell (2s¹ 2p¹).
- To form two sigma bonds (one with the other carbon and one with hydrogen) and one pi bond, carbon must promote one electron from the 2s orbital to the empty 2p orbital.
- This results in two unhybridized p orbitals (for pi bonding) and two sp hybrid orbitals (for sigma bonding).
Linear Geometry:
- The 180° bond angle between the carbon atoms confirms the sp hybridization, as sp hybrid orbitals arrange themselves linearly to minimize repulsion.
Sigma and Pi Bond Formation:
- The sp hybrid orbitals overlap with the hydrogen s orbital and the other carbon’s sp orbital to form sigma bonds.
- The remaining unhybridized p orbitals overlap side-by-side to form a triple bond (one sigma + two pi bonds).

Thus, the sp hybridization in $C X_{2} H X_{2}$ explains its linear structure and triple bond formation.

Discussion