Hybridization of the carbon atom

In bond formation different atomic orbitals mix to give hybrid orbitals of equal shape and energy; this is hybridization (the theory was proposed by L. Pauling in 1931). In sp³ hybridization one s and three p orbitals mix: four equal orbitals point toward the corners of a tetrahedron, with an angle of 109°28′; such carbon is found in methane and all alkanes and forms four σ-bonds. In sp² hybridization one s and two p orbitals give three orbitals in one plane at 120°; the unhybridized p-orbital stands perpendicular to the plane and forms a π-bond (ethylene, benzene, carbonyl group). In sp hybridization one s and one p orbital mix: two orbitals at 180° (a linear molecule) and two p-orbitals form two π-bonds (acetylene, propyne, a carbon with a triple bond). A quick rule for the hybrid state of carbon: only single bonds — sp³; one double bond — sp²; a triple bond or two double bonds — sp.