Question

Which of the following is not an actinide.

• A. Curium
• B. Californium
• C. Uranium
• D. Terbium

Answer 1

Answer: (D)

Terbium

Answer 2

Terbium is lanthanide as it belongs to $4f -$series having configuration $\lbrack Xe\rbrack 4s^{9}6s^{2}$.

However the remaining members belong to $5f -$series (actinides).