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A negatively-charged subatomic particle. One of 3 main subatomic particles (parts of an atom). Electrons are negatively-charged and they hang out in an “electron cloud” around the dense central nucleus where the protons and neutrons live. Electrons move around a lot so you never know exactly where one will be, but there are places where you’re more likely to find them and these places are often depicted in shells or more accurately in “orbitals.” The outermost electrons (furthest from the attractive pull of the positively-charged nucleus) are called valence electrons and they are the most energetic. Atoms can lose valence electrons to form cations (positively-charged particles) or share valence electrons to form strong bonds called covalent bonds.