Information
n-Butane: molecular shape and London dispersion forces
n-Butane and isobutane both have the molecular formula C4H10. They are non-polar alkanes, so they have neither a permanent dipole nor a permanently charged side.
Nevertheless, the molecules briefly attract one another: the electron cloud is never distributed completely evenly. The motion of the 26 valence electrons creates local temporary partial charges, which induce corresponding charge shifts in neighbouring molecules. These weak, short-lived attractions are called London dispersion forces.