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

Though numerous lanthanides possess radioactive isotopes, most lanthanoids are not. Radioactivity in lanthanoids is confined to specific isotopes, such as certain isotopes of promethium, thus invalidating option (D). The remaining assertions are valid; for instance, lanthanides display a trend of decreasing ionic radius from La$^{3+}$ to Lu$^{3+}$ attributed to lanthanoid contraction.