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The existence of bubble nuclei identified by the central depletion in nucleonic density is studied for the conventional magic N (Z) = 8, 20, 28, 40, 50, 82, 126 isotones (isotopes) and recently speculated magic N = 164, 184, 228 superheavy isotones. Many new bubble nuclei are predicted in all regions. Study of density profiles, form factor, single particle levels and depletion fraction (DF) across the periodic chart reveals that the central depletion is correlated to shell structure and occurs due to unoccupancy in s-orbit (2s, 3s, 4s) and inversion of (2s, 1d) and (3s, 1h) states in nuclei upto Z ≤ 82. Bubble effect in superheavy region is a signature of the interplay between the Coulomb and nn-interaction and depletion fraction (DF) is found to increase with Z (Coulomb repulsion) and decrease with isospin. Our results are consistent with the available data. The occupancy in s-state in 34 Si increases with temperature which appears to quench the bubble effect.

Two-proton radioactivity with 2p halo is reported theoretically in light mass nuclei A = 18-34. We predict 19 Mg, 22 Si, 26 S, 30 Ar and 34 Ca as promising candidates of ground state 2p-radioactivity with S 2p < 0 and S p > 0. Observation of extended tail of spatial charge density distribution, larger charge radius and study of proton single particle states, Fermi energy and the wave functions indicate 2p halo like structure which supports direct 2p emission. The Coulomb and centrifugal barriers in experimentally identified 2p unbound 22 Si show a quasi-bound state that ensures enough life time for such experimental probes. Our predictions are in good accord with experimental and other theoretical data available so far.