Which of the following is not an actinoid?
(i) Curium (Z = 96)
(ii) Californium (Z = 98)
(iii) Uranium (Z = 92)
(iv)Terbium (Z = 65)
The answer is the option (iv) Terbium (Z = 65)
Explanation: Actinoids are the elements with Z= 90 to 103, and they are characterised by the outer electronic configuration . In an actinoid the last electron enters the f-orbital, and that is not the case in Terbium, and hence it is not an actinoid, but it is a lanthanoid.