The lanthanides and actinides belong to the inner transition metals from "summary" of The Periodic Table: A Very Short Introduction by Eric R. Scerri
The lanthanides and actinides are two sets of elements that are placed separately at the bottom of the periodic table, beneath the main body of elements. They are known as inner transition metals because they exhibit similar chemical properties to the transition metals, which are located in the d-block of the periodic table. However, the lanthanides and actinides have unique characteristics that set them apart from the rest of the elements. One key feature of the lanthanides and actinides is their electron configurations. These elements have partially filled f-orbitals, which gives them their distinctive properties. The f-orbitals are located in the innermost shells of the atoms, which is why these elements are called inner transition metals. The presence of the f-orbitals allows the lanthanides and actinides to form a wide variety of compounds with different oxidation states. Another important characteristic of the lanthanides and actinides is their tendency to exhibit lanthanide and actinide contraction. This phenomenon refers to the decrease in size of the atoms as you move across the series. This contraction is due to the poor shielding of the f-electrons, which leads to greater nuclear attraction and a smaller atomic radius. As a result, the lanthanides and actinides have similar atomic sizes despite being in different rows of the periodic table. The lanthanides and actinides also have high atomic numbers, which means that they have a large number of protons and electrons. This results in the formation of complex ions and compounds with unique properties. The lanthanides, in particular, are known for their bright colors and magnetic properties, while the actinides are often radioactive and have important applications in nuclear energy and medicine.- The lanthanides and actinides belong to the inner transition metals because of their electron configurations, lanthanide and actinide contraction, high atomic numbers, and unique chemical properties. These elements play a crucial role in the periodic table and have diverse applications in various fields.
