  Description of a nuclear system in its ground state and at low excitations
based on the equation of state (EoS) around normal density is presented. In the
expansion of the EoS around the saturation point additional spin polarization
terms are taken into account. These terms, together with the standard symmetry
term, are responsible for appearance of the $\alpha$-like clusters in the
ground state configurations of the N=Z even-even nuclei. At the nuclear surface
these clusters can be identified as alpha particles. A correction for the
surface effects is introduced for atomic nuclei. Taking into account an
additional interaction between clusters the binding energies and sizes of the
considered nuclei are very accurately described. The limits of the EoS
parameters are established from the properties of the $\alpha$, $^{3}$He and
$t$ particles.
