charge - How exactly do protons and electrons interact with each other?

How do these particles exchange information about charge and position between themselves, even though there's mostly empty space between them?

Also what happens if a free electron passes closer to a nucleus of a hydrogen atom than its own electron?

My random guesses so far:

1. Proton won't react because it's somehow locked with its existing electron


2. Proton will catch it and release the previous one


3. Proton will catch it and keep both of them with half the force


4. Existing electron will simply repel incoming one


5. Something else?

Answer

The proton and electron exchange information via a gauge boson, in this case, a virtual photon. This is how the electromagnetic interaction is mediated.

As for your other question, the electron will get decelerated and deflected and emit a photon, releasing some of its energy in a process called Bremsstrahlung