  The ground state properties of the two-electron atom with atomic number
$Z\geq 2$ in the spherical vacuum cavity with general boundary conditions of
"not going out" are studied. It is shown that for certain parameters of the
cavity such atom could either decay into the one-electron atom with the same
atomic number and an electron or be in stable state with the binding and
ionization energies several times bigger than the same energies of the free
atom. By analogy with the Wigner-Seitz model of metallic bonding, the
possibility of the existence of such effects on the lattice formed by the
vacuum cavities filled with the two-electron atoms of the same type is
discussed.
