With a new parameterization of potential parameters which reproduces the gr
ound state properties of shell closed nuclei fairly accurately, the role of
occupancy of 2s(1/2) level in determining the halo structures of O-17, N-1
6, C-15, B-14, Be-13 have been investigated. The results show interesting c
ross over of level occupancies which may explain the increase in interactio
n radii.