Chemistry Class 12 NCERT Solutions: Chapter 8 The d and f Block Elements Part 11

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Q: 9. Explain why ion is not stable in aqueous solutions?


In an aqueous medium, is more stable than . This is because although energy is required to remove one electron from , high hydration energy of compensates for it. Therefore, ion in an aqueous solution is unstable. It disproportionate to give and .

Q: 10. Actinoid contraction is greater from element to element than lanthanoid contraction. Why?


In actinoids, orbitals are filled. These orbitals have a poorer shielding effect than orbitals (in lanthanoids). Thus, the effective nuclear charge experienced by electrons in valence shells in case of actinoids is much more that that experienced by lanthanoids. Hence, the size contraction in actinoids is greater as compared to that in lanthanoids.

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