Compare the chemistry of the actinoids with that of lanthanoids with reference to:
electronic configuration
Electronic Configuration: In lanthanoids, the 4f orbitals are being filled, while in actinoids, the 5f orbitals are being occupied. The 5f electrons penetrate less into the inner core of electrons compared to 4f electrons of lanthanoids. As a result, the 5f electrons are more effectively shielded from the nuclear charge than the 4f electrons of corresponding lanthanoids.
oxidation states and
Oxidation States: Actinoids display a wide range of oxidation states compared to lanthanoids. As shown in Table 4.11, actinoids exhibit oxidation states from +3 to +7 (e.g., U shows +3, +4, +5, +6 states). This wide range makes the chemistry of actinoids much more complicated. Lanthanoids primarily show +3 oxidation state, with few exceptions like Cerium showing +4 state.
chemical reactivity.
Chemical Reactivity: The ionisation enthalpies of early actinoids are lower than those of early lanthanoids. Since the outer electrons in actinoids are less firmly held, they are more available for bonding. This makes actinoids more reactive. Additionally, the radioactivity of actinoids creates special problems in their study. The chemistry of actinoids is more complicated due to variable oxidation states and radioactivity issues.
Explanation
This question tests understanding of key differences between lanthanoids and actinoids. The textbook explains that 5f orbitals (actinoids) penetrate less into the inner core than 4f orbitals (lanthanoids), affecting shielding. The oxidation state table clearly shows actinoids have multiple oxidation states (+3 to +7), making their chemistry more complex. Lower ionisation enthalpies in actinoids make outer electrons more available for bonding, increasing reactivity.