Transition elements are characterized by partially filled (n-1) d subshells.
Zn, Cd and Hg are not regarded as transition elements as they have completely filled (n-1)d subshell.
The electronic configuration of zinc is [Ar]3d104s2.
The electronic configuration of cadmium is [Kr]4d105s2.
The electronic configuration of mercury is [Xe]5d106s2.