Actinoids.

Atomic numbers of Actinoides are from ____

(i) Give the formula which expresses the general electronic configuration of actinoids. (ii) Which complexes are formed when actinoid halides react with alkali metal halides? (iii) Why do actinoids get tarnished in air.

What is Actinoid contraction ? Explain it.

The first member of actinoid series is____________.