  The spatial dispersion of the single-nucleon wave functions is analyzed using
the self-consistent mean-field framework based on nuclear energy density
functionals, and with the harmonic oscillator approximation for the nuclear
potential. It is shown that the dispersion depends on the radial quantum number
n, but displays only a very weak dependence on the orbital angular momentum. An
analytic expression is derived for the localization parameter that explicitly
takes into account the radial quantum number of occupied single-nucleon states.
The conditions for single-nucleon localization and formation of cluster
structures are fulfilled in relatively light nuclei with $A \leq 30$ and $n=1$
states occupied. Heavier nuclei exhibit the quantum liquid phase of nucleonic
matter because occupied levels that originate from $n > 1$ spherical states are
largely delocalized. Nevertheless, individual $\alpha$-like clusters can be
formed from valence nucleons filling single-particle levels originating from
$n=1$ spherical mean-field states.
