Q. In context of the lanthanoids, which of the following statements is not correct?
A) There is a gradual decrease in the radii of the members with increasing atomic number in the series.
B) All the members exhibit +3 oxidation state.
C) Because of similar properties the separation of lanthanoids is not easy.
D) A vailability of 4$f$-electrons results in the formation of compounds in +4 state for all members of the series.
Explanation
(d)
A) There is gradual decrease in the radii of the lanthanoids with increasing atomic number-a case of lanthanide contraction, thus true.
B) Ionization potential for the formation of ${Lu}^{3 +}$ is comparatively low, hence +3 state is favourable, thus true.
C) Due to lanthanide contraction $-$Zr and Hf; Nb and Ta, Mo and W have the same size and thus similar propertites and thus separation is not easy , thus true.
D) Formation of +4 state requires very high energy, thus incorrect.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.