Question

Out of the following statements, the incorrect statement is:

• A. La is actually an element of transition series.
• B. Zr and Hf have almost identical atomic radii because of lanthanoid contraction.
• C. Ionic radius decreases from La$^{3+}$ to Lu$^{3+}$ ion.
• D. Lanthanoids are radioactive in nature.

Hint:

Lanthanoids are generally not radioactive, except for specific isotopes. Keep in mind the lanthanoid contraction when considering trends in the series.

Answer 1

The Correct Option is D

While many of the lanthanides have radioactive isotopes, the majority of lanthanoids are not radioactive. Only some of the isotopes of lanthanoids, like certain isotopes of promethium, are radioactive. Therefore, option (D) is incorrect. The other statements are correct, as lanthanides exhibit trends such as the ionic radius decreasing from La$^{3+}$ to Lu$^{3+}$ due to lanthanoid contraction.