Guten Tag,

Once the capacitor is fully charged, the electrons will tend to concentrate at the surface of the negatively charged plate, because they will experience the attractive force of the positively polarized plate. Atomically speaking the electrons are still very much in the volume of the plate. Still, from a macroscopic perspective you can say they are all at the surface, but I would stop short of saying they are on the surface. Don't forget that the electrons will be equally rarified from the same region of the positively polarized plate, and you won't think of them as being removed from on the surface.

The inertia of the electrons don't really matter. The migration (or flow) of the electrons through the volume of the conductor is dominated by collisions, not free motion. This is why the electron flow in an electrical current is so slow. In a sufficiently rarified vacuum this would be different. But the volume of a conductor is not a sufficiently rarified vacuum.

As for how many electrons are involved, and how long it takes, those are well known quantifiable numbers. The total charge, Q, can be calculated as the product of the capacitance, C, and the voltage, V.

Q = CV

The charge of an electron is 1.602E-19 coulombs, so the total number of electrons involved is

CV/1.602E-19

As for how long this takes, the imbalance does not form linearly. It's an exponential curve. The charge of the capacitor as a function of time can be written as

Q(t) = CV(1 - exp(-t/RC))

where the quantity RC is defined as the time constant (imagine a little Greek letter tau here). Of course, as the charge increases so does the voltage dropped across the capacitor, which reduces the voltage dropped across the resistor and therefore the current flowing through it. So the current decreases exponentially.

In five time constants you'll have over 99% of the total capacity charged, (1 - exp(-5) = 0.993). The point is that RC time constants are usually quite large compared to the speed of light time frame in which the E field and potential propogate through the conductors.

Joe