6. Number of σ bond(s) and π bond(s)

6.3. Sigma (σ) bond and Pi (π) bond | Ethene

Two diagrams are shown labeled, “a” and “b.” Diagram a shows two carbon atoms with three purple balloon-like orbitals arranged in a plane around them and two red balloon-like orbitals arranged vertically and perpendicularly to the plane. There is an overlap of two of the purple orbitals in between the two carbon atoms, and the other four purple orbitals that face the outside of the molecule are shown interacting with spherical blue orbitals from four hydrogen atoms. Diagram b depicts a similar image to diagram a, but the red, vertical orbitals are interacting above and below the plane of the molecule to form two areas labeled, “One pi bond.”

Sigma(σ) bond (a): Five σ bonds
o One C–C bond: Overlap of sp2 hybrid orbitals on the carbon atom with one sp2 hybrid orbital on the other carbon atom
o Four C–H bonds:  Overlap between the C atoms’ sp2 orbitals with s orbitals on the hydrogen atoms
Pi(π) bond  (b): One π bond
o Formed by the side-by-side overlap of unhybridized p orbitals on each carbon atom
o Two lobes of the π bond are above and below the plane of the σ system