  Relativistic calculations of the electronic structure of the superheavy
element of the eighth period $-$ eka-francium ($Z=119$) and its homologues,
which form the group of alkali metals, are performed in the framework of the
configuration-interaction method and many-body perturbation theory using the
basis of the Dirac-Fock-Sturm orbitals (DFS). The obtained values of the
ionization potentials, electron affinities, and root-mean-square radii are
compared with the corresponding values calculated within the non-relativistic
approximation. A comparison with the available experimental data and the
results of previous theoretical calculations is given as well. The analysis of
the obtained results indicates a significant influence of the relativistic
effects for the francium and eka-francium atoms, which leads to a violation of
the monotonic behaviour of the listed above chemical properties as a function
of the alkaline-element atomic number. In addition, the quantum electrodynamics
corrections to the ionization potentials are evaluated by employing the model
Lamb-shift operator (QEDMOD).
