What are actinide ? Give three example .

Explanation

(i) The fourteen elements following actinium, i.e., from thorium (Th) to lawrentium (Lr) are called actinoids.
(ii) All the actinoids are radioactive and most of them have short half lives.
(iii) The heavier members being extremely unstable and not of natural occurrence. They are produced synthetically by the artificial transformation of naturally occuring elements by nuclear reactions.
(iv) Example : Thorium, Uranium, Plutonium, Californium.