Question
Answer the following questions:

- The figure given alongside illustrates the first ionization enthalpies of first, second and third series of transition elements. Answer the question that follows:
- Which series amongst the first, second and third series of transition elements have the highest first ionization enthalpy and why?
- Separation of lanthanoid elements is difficult. Explain.
- $Sm^{2+}, Eu^{2+}$ and $Yb^{2+}$ ions in solutions are good reducing agents but an aqueous solution of $Ce^{4+}$ is a good oxidising agent. Why?

