Abstract :
The present contribution focuses on few recent experimental achievements related to the study of the N=28 shell closure south to the doubly magic nucleus 4820Ca. It is shown that a gradual change from spherical to deformation occurs in the N=28 isotones from Z=20 to Z=14. This feature is ascribed to specific proton-neutron interactions, such as tensor forces, and to the posibility to develop quadrupole correlations between the occupied and valence states.
