Which one of the following statements related to lanthanoids is incorrect?
- Europium shows +2 oxidation state.
- The basicity decreases as the ionic radius decreases from Pr to Lu.
- All the lanthanons are much more reactive than aluminium.
- Ce(+4) solutions are widely used as oxidizing agent in volumetric analysis.
Answer
(3) All the lanthanons are much more reactive than aluminium.
Solution
(1) Correct: Eu shows +2 state (4f7).
(2) Correct: due to lanthanoid contraction, the ionic size and hence the basicity of the hydroxides decrease from La to Lu.
(3) Incorrect: as per NCERT, the earlier members of the series are quite reactive, similar to calcium, but with increasing atomic number they behave more like aluminium.
(4) Correct: as per NCERT, Ce(IV) is a strong oxidant and is used as an analytical reagent.
Answer: (3)