  The ground and some excited states of the Li atom in external uniform
magnetic fields are calculated by means of our 2D mesh Hartree-Fock method for
field strengths ranging from zero up to 2.35 10^8 T. With increasing field
strength the ground state undergoes two transitions involving three different
electronic configurations: for weak fields the ground state configuration
arises from the field-free 1s^22s configuration, for intermediate fields from
the 1s^22p_{-1} configuration and in high fields the 1s2p_{-1}3d_{-2}
electronic configuration is responsible for the properties of the atom. The
transition field strengths are determined. Calculations on the ground state of
the Li+ ion allow us to describe the field-dependent ionization energy of the
Li atom. Some general arguments on the ground states of multi-electron atoms in
strong magnetic fields are provided.
