Electrons in an atom are located in regions called electron shells or orbitals that surround the atom's nucleus. These shells are organized in layers at different distances from the nucleus, with electrons occupying various energy levels within these shells. Electrons do not orbit the nucleus like planets around the sun but exist in a cloud-like distribution where the likelihood of finding an electron is described by quantum mechanics. The closest shell to the nucleus can hold up to 2 electrons, the next up to 8, and so on, with each shell corresponding to specific energy levels and subshells. Electrons in outer shells have higher energy than those closer to the nucleus and are responsible for chemical behavior and bonding.

In summary, electrons are found outside the nucleus in shells or orbitals that form a cloud around the nucleus, with defined energy levels and probabilities rather than fixed paths.