ABSTRACT
Double Bond = one sigma-type bond plus one pi-type bond
Triple Bond = one sigma-type bond plus two pi-type bonds
a. A sigma bond is an end-to-end overlap of orbitals which provides a spherically symmetrical electron-density distribution around the bond axis; it allows bonded atoms to rotate around the bond axis. All orbital types can engage in end-to-end overlap: s, p, d, sp-hybridized, sp2-hybridized, sp3-hybridized, etc. Hybridized orbitals always form sigma-bonds, never pi-bonds.
