What are the characteristics of the transition elements and why are they called transition elements? Which of the d-block elements may not be regarded as the transition elements ?

Explanation

Characteristics of the transition elements : The d-block elements are called transition elements because these elements represent change (or transition) in properties from the most positive electropositive s-block elements to the least electropositive p-block elements.
The electronic configuration of Zn, Cd and Hg are represented by the general formula `(n - 1)d^(10) ns^(2).` The orbitals in these elements are completely filled in the ground state as well as in their common oxidation sates. Therefore, they are not regarded as transition elements.