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The d & f Block Elements — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryThe d & f Block Elements5 Marks
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. Sm2+, Eu2+ and Yb2+ ions in solutions are good reducing agents but an aqueous solution of Ce4+ 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 4fsubshell.
  2. This is due to lanthanoid contraction.
  3. Sm2+, Eu2+ and Yb2+ 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 Ce4+ gains one electron to attain +3. Hence, Ce4+ is an oxidising agent.

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