The ground state is the state lowest energy and that is the state of the ordinary configurations.
Alkali metals are the group 1 of the periodic table. All the alkali metals have 1 electron in their valence shell.
The configurations of the alkali metals are:
Li: [He] 2s
Na: [Ne] 3s
K: [Ar] 4s
Rb: [Kr] 5s
Cs: [Xe] 6s
Fr: [Rn] 7s.
As you see the electron configurations of the alkaly metals is the confiuration of the previous noble gas plus one electron that occupies the next s orbital.