Question

Which of the following belongs to the actinoids series of elements?

• A. $\mathrm{La}$
• B. $\mathrm{Lu}$
• C. $\mathrm{U}$
• D. $\mathrm{Sm}$

Answer 1

The correct option is C

$\mathrm{U}$

Explanation for correct option:

Actiniods:

• Actinoids are metallic chemical elements with atomic numbers from $89\mathrm{to}103$.
• $f$-block transition elements are lanthanoids and actinoids.
• The periodicity of these elements' electrical structures differs from the most stream, as seen by their placement in separate positions within the table.
• Actinide series members are radioactive and it is easy for actinoids to form complexes while lanthanides do not form complexes easily.

Uranium:

• Uranium is a chemical element with the symbol U and atomic number $92$.
• It is a silvery-grey metal in the actinide series of the periodic table.

Explanation for incorrect options:

Lanthum$\left(\mathrm{La}\right)$, Lutetium$\left(\mathrm{Lu}\right)$, and Samarium$\left(\mathrm{Sm}\right)$ all are the elements of Lanthanide series. Thus, options A, B, and D are incorrect.

Hence, the correct option is C.