  The odd-odd nucleus 210Bi is studied within the framework of the shell model
using effective two-body matrix elements derived from the CD-Bonn
nucleon-nucleon potential. The experimental energies of the proton-neutron
multiplet ph9/2 ng9/2 are remarkably well reproduced by the theory, which
accounts for the 1- state being the ground state instead of the 0- predicted by
the Nordheim strong coupling rule. It is shown that the core-polarization
effects are crucial to produce this inversion. The similarity between
neutron-proton multiplets in the 132Sn and 208Pb regions is discussed in
connection with the effective interaction.
