Monopole, quadrupole and pairing: a shell model view

The three main contributions to the nuclear Hamiltonian-monopole, quadrupol e and pairing - are analyzed in a shell model context. The first has to be treated phenomenologically, while the other two can be reliably extracted f rom the realistic interactions. Due to simple scaling properties, the reali stic quadrupole and pairing interactions eliminate the tendency to collapse of their conventional counterparts, while retaining their basic simplicity .