Electrons tend to settle in the lowest energy state available to them. This means that they will occupy orbitals that are closest to the nucleus and have the lowest energy. In an atom, the electrons are arranged in shells, with each shell containing a specific number of orbitals. The first shell, closest to the nucleus, contains two orbitals, while the second shell contains eight orbitals, and so on. Electrons fill these orbitals in a way that minimizes the total energy of the atom.