Transition elements are strictly defined by the presence of an incompletely filled d-subshell. Which — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Transition elements must have partially filled d-orbitals in their neutral atom or stable oxidation states. Elements with $(n-1)d^{10} ns^2$ (Group 12: $Zn, Cd, Hg$) have fully filled d-subshells and are not true transition elements. Configurations $ns^2 np^5$ and $ns^2 np^6$ belong to p-block halogens and noble gases, respectively. $(n-1)d^5 ns^1$ is a transition element (e.g., $Cr$).