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

Answer

  1. Third series has the highest first ionization energy due to poorest shielding effect of the fully filled $4$fsubshell.
  2. This is due to lanthanoid contraction.
  3. $Sm^{2+}, Eu^{2+}$ and $Yb^{2+}$ ions are good reducing agents as they tend to acquire common oxidation state of $+3$ shown by lanthanoids by the loss of one electron while $Ce^{4+}$ gains one electron to attain $+3$. Hence, $Ce^{4+}$ is an oxidising agent.

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