Knowing the orbitals of a particular species provides one information about the sizes, shapes, directions, symmetries, and energies of those regions of space that are available to the electrons (i.e., the complete set of orbitals that are available). This knowledge does not determine into which orbitals the electrons are placed. It is by describing the electronic configurations (i.e., orbital occupancies such as $$1s^22s^22p^2$$ or $$1s^22s^22p^13s^1$$) appropriate to the energy range under study that one focuses on how the electrons occupy the orbitals. Moreover, a given configuration may give rise to several energy levels whose energies differ by chemically important amounts. for example, the $$1s^22s^22p^2$$ configuration of the Carbon atom produces nine degenerate $$^3P \text{ states, five degenerate } ^1D \text{ states, and a single } ^1S$$ state. These three energy levels differ in energy by 1.5 eV and 1.2 eV, respectively.