question_answer 58)

    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) Fm

Answer:

                            (c) Tm (Z = 69) do not belong to actinoid series. The actinoid series is with atomic numbers 90 to 103. Thulium (Tm) has atomic number 69 belongs to lanthanoids (4f series).