They do not “revolve around the nucleus.” This model was abandoned by physicists over a century ago.
They are a kind of standing wave that is attracted to the nucleus. The standing wave is larger than the nucleus and cannot be sucked into. The electron fills a volume around the nucleus in a quantum mechanical manner.
There are many possible standing waves around a nucleus with different energies. These can be compared to the harmonics found on a drumhead. Each harmonic can only be occupied by one electron due to the Pauli Exclusion Principle. Because of this long-discarded model, successive electrons can occupy successive harmonics, which are unfortunately sometimes called orbitals.