Question

There are 14 elements in actinoid series. Which of the following elements does not belong to this series?

• A. $U$
• B. $Np$
• C. $Tm$
• D. $Pm$

Answer 1

The correct option is C $Tm$

Thulium $\left(Tm\right)$ has atomic number 69, and actinoid series has elements from atomic number 90-103.

Thulium belongs to lanthanoid series .

Hence, option C is correct.