(i) The three electrons present in 2p subshell of nitrogen remain unpaired because 2p sub shell contains three orbitals 2px , 2py and 2pz , of same energy so according to Hund's rule of maximum multiplicity, pairing of electrons in the orbitals belonging to the same subshell does not take place until each orbital belonging to that subshell is singly occupied.
(ii) Cr has configuration 3d54s1 and not 3d44s2 because in configuration 3d54s1 , 3d, shell is half-filled which is more stable configuration as compared to partially filled configuration.
