Chemistry · Structure of atom

In R.A. Millikan's oil drop experiment, the magnitude of electrical charge \( q \) on the droplets is always an integral multiple of the electrical charge \( e \), represented as \( q = n e \). What are the possible values of \( n \)?

1. \( n = 0, 1, 2, 3, \dots \)
2. \( n = \pm 1, \pm 2, \pm 3, \dots \)
3. \( n = 1, 2, 3, \dots \)
4. \( n = 0.5, 1, 1.5, 2, \dots \)