Triple bond

Bonding

Triple bonding can be explained in terms of orbital hybridization. In the case of acetylene, each carbon atom has two sp-orbitals and two p-orbitals. The two sp-orbitals are linear, with 180° bond angles, and occupy the x-axis in the cartesian coordinate system. The p-orbitals are perpendicular to the sp-orbitals on the y-axis and the z-axis. When the atoms approach each other, the sp orbitals overlap to form an sp-sp sigma bond. At the same time the p_z-orbitals approach and together they form a p_z-p_z pi-bond. Likewise, the other pair of p_y-orbitals form a p_y-p_y pi-bond. The result is formation of one sigma bond and two pi bonds. However, with heavy enough atoms, relativistic effects comes into play and one ends up, not with pure sigma and pi bonds for the three bonds, but rather hybridizations of sigma and pi bonds.

In the bent bond model, the triple bond can also formed by the overlapping of three sp³ lobes without the need to invoke a pi-bond.