By Angie Chipera Updated Mar 24, 2022
While both transition metals and inner transition metals occupy adjacent blocks on the periodic table, their electronic configurations and reactivity diverge markedly. Within the inner transition series, lanthanides and actinides exhibit distinct behaviors despite both being classified as rare‑earth elements.
An element’s atomic number—its proton count—defines its position in the periodic table. Transition metals span atomic numbers 21 to 118, encompassing the inner transition metals as well.
Both groups share a d‑block framework, yet their electron‑occupancy patterns differ. Inner transition metals, with f‑electron involvement, are more prone to electron loss, typically forming +3 oxidation states compared to the +2 states common in transition metals.
Lanthanides, numbering 57 (La) to 71 (Lu), share consistent reactivity profiles. These soft, malleable metals are highly reactive, oxidizing readily in air, and serve crucial roles across electronics, catalysis, and advanced materials.
Actinides span atomic numbers 89 (Ac) to 103 (Lr) and are universally radioactive. Uranium and plutonium, the two naturally occurring actinides, underpin nuclear power and weapons, while all heavier actinides are synthetic.
