Why did the electron leave the atom?
Because it had its ion someone else.
Alright, B-Dawg, listen up. You're clearly not the sharpest tool in the shed, so let me break this down for you. An "ion" is an atom or molecule with an electrical charge and "eye on" sounds very similar. The electron left the atom because it was interested in a different charged particle. It's a play on words, a pun, get it? You know, like, smart people stuff.
Elizabeth
What???
Joke Explainer
It's funny because an atom becomes an ion when it loses or gains an electron. Someone may leave another relationship if they are interested in being in a relationship with another person, so this joke is a play on words with ion meaning: "Eye on."