Question

Which of the following statements related to lanthanoids is incorreect?

• A. Lanthanoids are silvery white soft metals
• B. Samarium shows +2 oxidation state
• C. Ce⁺⁴ solutions are widely used as oxidising agents in titrimetric analysis
• D. Colour of Lanthanoid ion in solution is due to d–d transition

Answer 1

The Correct Option is D

The question asks us to identify the incorrect statement related to lanthanoids. Let's evaluate the options:

• (A) Lanthanoids are silvery white soft metals: This statement is correct. Lanthanoids are indeed soft, silvery white metals.
• (B) Samarium shows +2 oxidation state: This statement is correct. Samarium can show a +2 oxidation state, though it also commonly exists in the +3 oxidation state.
• (C) Ce+4 solutions are widely used as oxidising agents in titrimetric analysis: This statement is correct. Ce(IV) solutions are indeed used as oxidizing agents in titrations.
• (D) Colour of Lanthanoid ion in solution is due to d–d transition: This statement is incorrect. The color of lanthanoid ions in solution is due to f–f transitions, not d–d transitions as seen with transition metals.

The incorrect statement is (D) Colour of Lanthanoid ion in solution is due to d–d transition.

Answer 2

Lanthanoids typically have 4f electrons, and the color observed in their solutions is due to f–f transitions, not d–d transitions.  

• Option (A) is correct as lanthanoids are indeed silvery white soft metals.
• Option (B) is correct because samarium can show the +2 oxidation state, though it is less common.
• Option (C) is correct as Ce⁴⁺ is a strong oxidizing agent.
• Option (D) is incorrect as the color is due to f–f transitions, not d–d.