Originally the name transition metals was derived
from the fact that their chemical properties were
transitional between those of s and p-block elements Now according to IUPAC, transition metals are defined
as metals which have incomplete d subshell either in
neutral atom or in their ions Zinc, cadmium and
mercury of group 12 have full d
10 configuration in their
ground state as well as in their common oxidation states
and hence, are not regarded as transition metals However, being the end members of the 3d, 4d and 5d
transition series, respectively, their chemistry is studied
along with the chemistry of the transition metals