In the oil drop experiment,

all the drops had a charge equal to –1.60 × 10^–19 C.

all the drops were assumed to have adsorbed the same number of electrons.

since each drop likely adsorbed a different number of electrons, the charge on each drop had to be a multiple of the electron’s charge.

some of the drops contained fractions of electrons.

drops of oil were passed through a very thin film of gold atoms and their behavior was observed.