  In this work, we identify a unique and novel feature of central density
depletion in both proton and neutron named as doubly bubble nuclei in
50$\leq$Z(N)$\leq$82 region. The major role of 2d-3s single-particle (s.p.)
states in the existence of halo and bubble nuclei is probed. The occupancy in
s.p. state 3s$_{1/2}$ leads to the extended neutron density distribution or
halo while the unoccupancy results in the central density depletion. By
employing the Relativistic Mean-Field (RMF) approach along with NL3* parameter,
the separation energies, single-particle energies, pairing energies, proton,
and neutron density profiles along with deformations of even-even nuclei are
investigated. Our results are in concise with few other theories and available
experimental data. Emergence on new shell closure and the magicity of
conventional shell closures are explored systematically in this yet unknown
region.
