NEETChemistryd and f Block Elements
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Ce ⁴⁺ and Tb ⁴⁺ both act as strong oxidising agents in aqueous solutions. Reason (R): Both Ce ⁴⁺ and Tb ⁴⁺ are diamagnetic in nature. In the light of the above statements, choose the most appropriate answer from the options given below:
Options
- ABoth (A) and (R) are true and (R) is the correct explanation of (A)
- BBoth (A) and (R) are true but (R) is not the correct explanation of (A)
- C(A) is false but (R) is true
- D(A) is true but (R) is false
Correct answer
D. (A) is true but (R) is false
Step-by-step solution
Assertion (A) is true: Both Ce ⁴⁺ and Tb ⁴⁺ act as strong oxidising agents because they tend to gain one electron to achieve the more common and stable +3 oxidation state of lanthanoids. Reason (R) is false: The electronic configuration of Ce (Z = 58) is [ Xe ] 4f¹ 5d¹ 6s² , so Ce ⁴⁺ is [ Xe ] 4f⁰ , which has no unpaired electrons and is diamagnetic. However, the electronic configuration of Tb (Z = 65) is [ Xe ] 4f⁹ 6s² , so Tb ⁴⁺ is [ Xe ] 4f⁷ . It has 7 unpaired electrons and is highly paramagnetic. Therefore, (A