• question_answer 75)   All transition elements are d-block elements, but all the d-block elements are not transition elements. Explain.

Transition elements are regarded as those elements which possess partially filled penultimate d-subshell in their ground state or in one of their commonly occurring oxidation states. This definition does not cover zinc metals, i.e., the elements of group 12 which are considered as the end members of four d-block series. In each d-block series, the penultimate d-orbitals are successively filled. The general electronic configuration of el-block elements is : $(n-1){{d}^{1-10}}n{{s}^{0,1or\,2}}$ Thus, all the transition metals are d-block elements but all the d-block elements are not transition metals.