  Fermion localization functions are used to discuss electronic and nucleonic
shell structure effects in the superheavy element oganesson, the heaviest
element discovered to date. Spin-orbit splitting in the $7p$ electronic shell
becomes so large ($\sim$ 10 eV) that Og is expected to show uniform-gas-like
behavior in the valence region with a rather large dipole polarizability
compared to the lighter rare gas elements. The nucleon localization in Og is
also predicted to undergo a transition to the Thomas-Fermi gas behavior in the
valence region. This effect, particularly strong for neutrons, is due to the
high density of single-particle orbitals.
