This is because the electron is not actually a point particle spinning around in a defined orbit like you were taught.
Instead the electron is sort of smeared out across a volume in which there is some fractional chance of finding the qualities that make up an electron. It exists and doesn’t exist at any given point all through that volume, and as that volume is centered on the nucleus you can think of it as being “in contact” with the nucleus as much as possible. Adding more electrons into the mix creates [really interesting probability field interactions](https://en.wikipedia.org/wiki/Atomic_orbital#/media/File:Hydrogen_Density_Plots.png).
One weird implication of this is that the probability field doesn’t really “end” at any point on the edges, it is just the probability of encountering that electron becomes arbitrarily small. Conceptually though there is an infinitesimally small chance of interacting with any electron anywhere in the universe!
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