Question

Which of the following is not an actinoid?

• A. Curium (Z = 96)
• B. Californium (Z = 98)
• C. Uranium (Z =92)
• D. Terbium (Z = 65)

Answer 1

Answer: (D)

Element from atomic number $89$ to $103$ are called actinoids. Thus, terbium $(Z=65)$ is not an actinoid.